So recently I've been playing in a Strange Aeons AP run. Our party is 9th level and we hit a location that is full of traps. One room we encountered was full of paintings. Three of the paintings had magical traps that reset every 24 hours. One cast Summon Monster VIII, one cast Otto's Irresistible Dance, and the last cast Bestow Curse. The paintings themselves had unsettling subjects, but not so distasteful that you'd want to burn them on sight. They are probably masterworks.
The traps are paintings. Paintings not permanently attached to the walls. These are magical traps that adventurers can take to a merchant and sell. Two of them are 8th level spells! Bestow Curse is a 3rd level spell.
The formula for determining the cost of creating resetting magical traps (instead of one use traps) is 500gp x caster level x spell level plus material cost x 100. Fortunately none of these spells has an expensive material component.
Bestow Curse: 500gp x 5 x 3 = 7500gp is fine to give as treasure to a 9th level party.
8th level traps: 500gp x 15 x 8 = 60,000 gp is way, way too much to be handing to a 9th level party!
These are the costs to create the traps. Cost is usually the value players receive from merchants when selling items. Market Price is usually double the cost to produce things that can't be made with Craft skill alone.
I strongly suggest you don't make traps portable because some Merchants should be interested in buying such items!
Twist: The gold pillar is the trap. Removing it collapses the room your in. Too bad, maybe your next character should put some points in Knowledge (Engineering).
Although gold probably isn't the best material for crafting pillars in the first place.
Honestly, these seem like fun ideas if you handle them well.
Bestow Curse is actually a level 2 Medium spell. That makes the cost 4000 gp.
Irresistable Dance is a 6th level Bard spell. That makes the cost 48000 gp.
Summon Monster VIII is a 6th level Summoner spell. That makes the cost 48000 gp.
It might not be the correct way to price them but it reduces the profits to 100000 gp, or 25000 gp per party member. That's still too much though.
You might want to post this in the Strange Aeons forum to see how other GMs handled this.
Twist: The gold pillar is the trap. Removing it collapses the room your in.
That's not a trap, that's the default function of a pillar.
If you set the price too low, the PCs might just use the paintings in battle - point them at an enemy to send an Elder Elemental to fight them while they dance around helplessly.
That was my first thought, right when I read the thread title.
Bestow Curse may be saleable. Irresistible Dance is good, but only in conjunction with something else, or it will just wear off and then what?
SM 8 is a trickier one. As a GM, I'd rule that the summoned monster obeys the original creator's intent, or is uncontrolled, and is itself selected by the creator not the owner. So at the very least the thing is incredibly dangerous, and potentially useless. You might hope that a Barbed Devil apprehends the intruders to your castle, only to be disappointed when an elder Fire Elemental burns the place to the ground instead. Or you get 1d4+1 Dire Sharks flapping about.
The monster(s) summoned should be set when the trap was created. That said...the summoner isn't there to order them. As a trap you could have the trap act as a summoner and give a single command, but it wouldn't be anything the new owner could change. Just because you now own the trap you aren't safe from its effects.
But you know about the trap, so you can place it in such a way that you'd never trigger it. Only someone that isn't familiar with the room would investigate.
Which means you're going to lose a lot of servants, but they shouldn't be snooping around your private vault or escape tunnel anyways.
As long as you know about Otto's Irresistible Dance you could use it as entertainment. Force your guests to dance. It could also be used against dangerous guests. Making the guests exhausted could give you an advantage in hostile negotiations.
And if you put in a trap room where you drop people in front of the summoning painting, and put the dance painting on the only exit that should be somewhat effective.