There is the non-trivial problem of actually moving that much gold into Maytag's "possession". Even if you could easily move it (say with magic), the way that amount has been played up in value I can't imagine that you can just drop it off at a convenient pan-continental bank chain (any bank that can absorb that much with no problem should have owners/stockholders with even more wealth and likely more money, and you'd expect yet more from high rulers, etc.). You'd need to spend money to guard it, or would preferably convert it into assets (businesses, property, estates, farms, mines, etc.) that will not decrease in value due to the inflation you're causing by spending it (although Maytag probably wouldn't be considering inflation due to her world, it would still be safer to spread the money out, and better to have the money be earning you money than to have it just sitting there in a pile awaiting an unfriendly sorcerer, dragon, or whatever can overwhelm your expensive, mandatory guards).
Lehm of course has a secret hideout and only associates with "trusted" people (or can just generate gold with magic, so he doesn't consider it a big risk, or only himself or himself and "super-trusted" people know the vault location(s)), so it would be convenient for him to hold onto that money in the form of gold, but Maytag can't exactly take possession if Lehm is the one who holds it, and I doubt Lehm would give up his location so easily unless he has another...perhaps he does (whether this is the location of the gold, or the gold is here and he'll just move there, I don't know). Either way, "giving" the gold while holding onto it is pretty flimsy, as Lehm could just take it "back" whenever, and I doubt the gold would be at a convenient location to withdraw sums of money from regularly.
Of course how he got the money and what Maytag's task is are important, too.