I consider myself a dwarf's dwarf, and so ever since I learned a bound djinn could produce valuable trade goods I have been intruiged by the prospect of using magic to make money. Unfortunately, my research has not been as fruitful as I had hoped.
Oh, I've found plenty of stories of mages performing spells inexchange for payment, or of clever plans that used magic as a means to profit, but when I said "using magic to make money," I meant 'make' in the purely literal sense: I want a magic item that conjures gold from thin air. Preferably permanent, nonmagical gold, though I would settle for a spell that creates something reasonably-valuable and easily sold. (Honestly, what I'd really like to get out of this is a purse that magically fills itself, to pass down to my decendants.)
Actually, designing such a magic item is fairly easy - I could use the 33:1 ratio to ensure it's not too cheap, at the very least. The real trick is coming up with the spell effect that the magic item should be based on, so that it can actually be created in the first place.
Alas, it's hard to find examples of spells that directly create permanent objects of value. (The closest I have discovered so far is the bless spell, which allows a priest to create 25 gp worth of holy water in exchange for a 10 gp sacrifice - and even then there are conditions attached: The priest must be over a certain level before the spell can be used in this way.) Unfortunately, there don't seem to be any effect costs or other guidelines I could use to estimate how high a level such a spell should be.
I therefore must ask: What would be an appropriate effect cost for a spell that creates objects or coin of a certain value?