Please forgive it this has been already answered, but I do the answer anywhere.
If I want to create an item which requires for me to know a spell, can I simply replace said spell with Wish or Miracle or do I have to take the +5DC in this case?
Provided I can, does the crafting cost increase when using Wish for this purpose? The item crafting description says something about access to the spells, not their use.
Can someone help me, please?
At the rules is you need the specific spell and no other spell Can stand in. But it is not a unreasonable houserule. That a spell that Can simulate the prerequsite spell Can be used instead.
There seems to be a few errors here.
First, you can create almost* every item in the book without using any spells at all, simply take the +5 DC and make what you want. If you DID use Wish instead, why would you use Wish AND take the +5 penalty? Strictly by RAW, it says you must cast the required spell daily during creation and Wish is NOT the required spell, so it probably should not work. However, Wish DOES duplicate (not "simulate") other spells so a duplication might suffice. This would be up to your GM, but if it does suffice, it would NOT also incur the +5 penalty.
Note that you must cast the spell once EACH DAY during creation. Wish requires 25,000gp diamonds each time it's cast. So if the item is worth 10,000gp, you will have to cast 10 Wish spells for a total of 250,000gp worth of diamonds. It's hard to imagine that this is worth it.
Before I wasted all that cash, I would use 5 Wish spells (only 125,000gp worth of diamonds) to raise my INT by 5 points which would perfectly offset the +5 DC penalty for creating items without the spell, then I would crate all the items I want and never cast any spells - all the while saving at least 125,000gp in diamonds I didn't waste to create that first little item AND reaping the rewards of being smarter: more skills, better save DCs if I'm a wizard (etc.), and going on Jeopardy to win back all the money I spent on diamonds.
*You cannot create potions, spell-trigger, or spell-completion magic items without casting the actual spell, so for these little guys, you cannot simply raise the DC by +5 and skip the spell casting. If you have no access to the spell needed, then I suggest go buy a few scrolls of it - that would certainly be far, far, FAR cheaper than casting a Wish spell.
Second, by RAW, the item's caster level is based on the spell required, not the spell used: "A creator can create an item at a lower caster level than her own, but never lower than the minimum level needed to cast the needed spell." So if you create an item that needs a Cure Light Wounds spell, then you can set the caster level as low as 1, or as high as your own level, or anywhere in between. Using a Wish to duplicate that Cure Light Wounds spell does not alter this rule.
For the spirit of the rules, the cost of wish should be added, as the process assumes that the spell is effectively cast during the item creation. All the magic items already include the cost of the materials of the required spells, for example writing a scroll of Wish costs the price of writing a scroll of a 9th-level spell plus 25000, that is the material (on the bright side that scroll can now be used without providing the material component)
Anyway the crafting rules allow you to employ other spellcasters and magic items that replicate spells in order to provide the required spells, so it may be more efficient to buy scrolls of the requisites.
DM, do you have a quote on that?
Note that you must cast the spell once EACH DAY during creation. Wish requires 25,000gp diamonds each time it's cast.
Hmmm, actually I need to revise my statement. It applies only to certain magical items: potions, scrolls, staves, and wands (with extra usage required for staves and wands).
Other types of items simply "trigger" the spell "as if it had been cast" but don't require the component. Which is how you can make a Ring of Three Wishes for only 97,500gp up front. (it really should be 97,950 but I guess they rounded to a prettier number - but if it actually required casting wish daily during the 23 days it takes to create this ring, that would add 575,000gp to the base price and the crafting price which clearly is not the case).