Lets not get into the genesis spell, I really don't want this derailed into arguments about what the spell actually means and I can tell its the kind of can of worms waiting to be opened.
Okay. Leaving aside Genesis, though, there are just a ridiculous number of ways that full-casters can generate essentially limitless conventional wealth. (And, well, if there weren't, I doubt there would be half as many threads about how to fix D&D economics. Maybe a third. ) The thing is, when you think through the implications of a full-caster being able to generate essentially limitless conventional wealth, the inevitable conclusion is that conventional wealth is valueless when dealing in items produced and desired by characters of sufficient level to access these methods, which is to say high-end magic items.