Context: my mortal character is trying to buy the assistance of a ghoul clan. I've talked them into accepting a deal, but they want a really ridiculous amount of gold. My character is rich, but not rich enough.
So we're thinking of having the wizard transmute a big pile of cheaper metal.
(If I were GMing I'd treat it as a Resources replacement and require extra shifts to make the transmutation last. 8 shifts base, plus duration. 16 shifts would suffice to make it last a year, so I'd charge 20ish shifts for permanency.
Of course, I'm a player so I'm a bit biased.)
Anyway, I think this has never been done in the books because it's hard, most Wizards don't particularly want more money, and it would make you look like a criminal if you suddenly pulled a bunch of gold out of nowhere.
Exactly this. Shifts equal to the skill replacement needed, plus a shift per step above the base duration "a day." Technically, since you're transmuting, you should be adding shifts in to make the gold pass an Alertness/Investigation check (one shift per level above Mediocre), but I think that's overkill.
It isn't shown in the books because Harry just doesn't think it's moral to do something like this. The White Council frowns upon creating gold willy-nilly because it upsets economies, but there are no rules against it. I think Harry actually alludes that the White Council has used its collective power and longetivity to create its fortunes by partially doing this, in fact.
I also recall Harry discussing the creation of gold when he's going over the reasons behind why the Laws disallow some things but allow others, in...Small Favor, I think?
For PCs creating gold, there are two main issues: disbursing the gold, and what happens once the enchantment ends on your "fool's gold." If they don't put the effort into really making it last a long time, make it come back to haunt them. If they don't take great pains to sell it off carefully, have that come back to haunt them.
In this specific case, you don't need to worry about the first issue, unless the ghouls question how you were able to get a hold of such a ridiculous amount. For the duration issue, Ghouls live a long time, but putting enough shifts in makes the ramifications of the duration extend past the scope of the game and thus irrelevant.