"In most cases, wizards charge a fee for the privilege of copying spells from their spellbooks. This fee is usually equal to half the cost to write the spell into a spellbook."
So the normal cost of writing a new spell x1.5.
For practical purposes you would think wizards would swap spells back and forth like baseball cards, but evidently not.
I generally find it easier to buy a scroll and scribe it, rather than hunt down another wizard. I've always been under the impression that while wizards don't mind selling off scrolls, they're disturbingly protective of their spellbooks. Which seems silly, when it comes down to it. Perhaps it's a matter of no one wanting to expose their awful penmanship?
I'd say that is pretty much a DM's call. Kind of depends on how magic is treated in the setting.
In some settings you get Wizard colleges where you can easily get instructions in new spells. In other settings wizards jealously guard their spells from rivals and are like as not to kill you for fear that you are going to steal their secrets.
Well finding out what the highest level spellcaster in a city is quite easy, in the city's stats you can see the highest level spell available. Now finding out if it's arcane or divine or both is another issue and you have to dig deeper for that.
For example Magnimar has 8th level spell as the highest level spell available in the city but if you search more you find out that while there is a 15th level wizard in Magnimar, the highest level cleric is only 13. So in Magnimar you have 8th level arcane spells but only 7th level divine spells.
Now keep in mind that you don't have to find a live wizard in order to copy from his spellbook, you can copy spells from a dead wizard's spellbook. That means that magic academies, guilds, noble families, churches etc. probably have a large collection of spellbooks and they might charge you a lot of money (as shown by the table) in order to look at them and copy them.
Keep in mind that some spells (evil spells mostly) are usually not allowed to be copied.
Now to answer your actual question, no unfortunately there isn't any system (that i am aware of) that helps you figure out an exact number (or even a rough number) on the number and/or highest level of spells that you can see and/or swap copy.
1)PC Wizard tells me he wants to fill his spellbook(s) with new spells from other wizards' and magi's spellbooks.
2)I figure out what's the highest level of spell he can copy (given what i know about the city like i wrote above) and i tell the player the maximum spell level.
3)Now comes the hard part, i try to figure out how many spells he can swap*, i look at the spellbook of the PC wizard and i try to come up with a number (or a die roll and a number).
4)I tell the player how many spell levels he can swap in any way he wishes**, for the rest of the spells he wants he has to pay the "fee".
5)I check the spells that the player ended up copying in order to make sure that he didn't take a spell that he shouldn't be able to copy (for example evil spells).
Keep in mind that all of the above require many hours if not days of search, talking, bargaining and in sort "working", and that doesn't even take into account the numerous hours needed for the actual scribing of spells.
*allow another wizard to see spells from his spellbook and in turn see from said wizard's spellbook, so that he doesn't have to pay the "see the spellbook fee"
**for example i tell him that he can swap 10 spell level, how he spends that number is his own issue, he can swap for 10 1st level spells, he can swap for 2 5th level spells or any other combination (subject to the limit of the highest level spell he can copy from the city)
@Liam Warner
Are you getting those numbers from somewhere in specific are they your own? If it's the latter what is your reasoning behind them? Because they seem way too low and not in accordance with what i know about Golarion (or rather the inner sea region).
"In most cases, wizards charge a fee for the privilege of copying spells from their spellbooks. This fee is usually equal to half the cost to write the spell into a spellbook."
So the normal cost of writing a new spell x1.5.
For practical purposes you would think wizards would swap spells back and forth like baseball cards, but evidently not.
Depends on the GM and setting.
If you look at most settings in the past you find that hording of magical knowledge was far more common than sharing spells for a paltry fee - this is something that extends across at least the first thirty years of the hobby. Both Greyhawk and Forgotten Realms were both famous for the stinginess of wizards with spell lore. Greyhawk wizards tended to only pass down spells to close friends or apprentices, while Forgotten Realms has entire plots centered around gaining access to powerful spells from wizards - or dying in the attempt. Even incredibly powerful archmagi specifically tasked by the goddess of magic were protective of their knowledge and reluctant to share it with strangers and those who had not proven themselves worthy of it.
Even if you don't tie in a specific setting there are plenty of practical reasons why a wizard (especially a more powerful one) would be discriminatory in his sale of spell knowledge. Many higher level spells are incredibly destructive, and in the wrong hands could wreck tremendous harm (even if that isn't the intent). All it takes is one idiot wizard dropping a fireball in a tavern brawl to sour a population to wizardry for a long time.
Beyond that, especially when it comes to sharing spellbooks instead of scrolls, you are basically trusting another individual with access to your most prized possession, source of your power, and likely the result of a lifetime of work and anchievement. The idea that something like that is shared for a minor fee has always been laughable to me.
This whole idea that you can buy spells with a degree of certainty for a specific price is a relatively new idea and (I think) mostly tied to a move away from setting specificity that came with 3x.
As a rule the best experience I've had with the entire process involved relatively easy access to lower level spells (3rd level and under) and increasingly hard to find high level spells that often require you seek out a specific individual and persuade them to share their lifetime worth of work. It meant that at low levels we could jump right from adventure to adventure pretty quickly without getting bogged down, while at higher levels it encouraged the fostering of relationships with other powerful spellcasters and often generated plots simply as a result of trying to get in their favor or as a result of proximity to them. That this also tends to prevent the potentially problematic 'wizard picks exactly what spells he feels are most optimal' idea makes it particularly appealing to me.
I generally find it easier to buy a scroll and scribe it, rather than hunt down another wizard. I've always been under the impression that while wizards don't mind selling off scrolls, they're disturbingly protective of their spellbooks. Which seems silly, when it comes down to it. Perhaps it's a matter of no one wanting to expose their awful penmanship?
What would you rather sell to a stranger: a scroll at a major profit it took you a few hours to scribe or access to your very fragile and most prized possession that you are potentially powerless without?
TL:DR - Ask your GM. It's going to vary by game and setting. There is no hard and fast rule. Some GMs hand wave it, others do not.
Depends on the GM and setting.
Everything depends on the GM and setting.
"In my world, there are no wizards."
"In my world, there are no spellbooks."
"In my world, there is no currency."
"I run my game as an erotically charged sexventure."
Hopefully your GM isn't draconian about it. The system stated here where you had to trade for all 6th level and higher spells makes wizards unplayable. At that point, the sorcerer knows more spells, casts more spells, and has more flexibility. Divine casters who don't have to care about a spellbook also operate at full power. This is why I make it easy for most spells most of the time.
In a large city, you should be able to find someone willing to let you copy most lower level spells. Higher level spells might be a bit more difficult, depending on the size of the city. It wouldn't be unreasonable for your GM to call for a diplomacy check (the gather information use) for you to find whom to talk to. But someone else in the party can be the one to make the check.
Personally, I usually just allow the PC to copy the spell if she's in a place with high enough level wizards. Knowledge is power and all that, but knowledge of fireball is already widespread. If I'm a wizard and someone comes to me wanting to pay to copy fireball, there's no benefit to saying no. That person will just go to the other wizard down the road and I won't get the spell-copying fee or the good will of the other wizard. 45 gp and cordial relations with other high level wizards are always good things. I do sometimes require the diplomacy check, if the circumstances warrant it. From a metagame perspective, throwing hurdles at the wizard learning new spells just slows down the game. Besides, clerics and druids don't have to go through ridiculous hoops to get their spells.
That said, remember that as a wizard you have spells to help you solve your problems, even if those problems are needing more spells in your spellbook. No one in the local city willing to share fireball with you? Teleport somewhere else.
If i remember right wizards can even learn spells from blood....
If i remember right wizards can even learn spells from blood....
That adventure writes itself. "Hey guys I need a high-level spell, so we gotta track down this high-level wizard and kill him so I can drink his blood. You know, when you have some downtime."
Select one spell available to the dead spellcaster (this must be a spell on your spell list)