I genuinely think my biggest problem with it, even bigger than the issue of being essentially just the guy that makes sure the fence isn't ripping them off when they go back to town until level six, is the fact that I really do see this character being the final repository of a huge amount of the party gold. It's like having an artificer, only even better, because you don't even need an item half the time. You can just whistle up the effect. I think a DM will end up having to dump money on a campaign to keep them from going broke or the players will need to really have an iron will to just not ever take the easy way out, or it is going to be a very slippery slope.
That all said, I have thought about it some and I am liking this. What if the wealth "Summoned" was "Pluto-bucks" or whatever. They are the only coinage useful for the exchange, which means they can be traded directly across for normal currency. They require that the Plutomancer spend his or her time in ritual, BUT unlike any other caster, the only real limit to how much power a Plutomancer can stockpile is how much time they are given to accumulate this special currency. This eliminate the problem with the other characters becoming money sponges. It allows the DM to sometimes be generous without fear that the next adventure will just be a complete cakewalk because of it, and it allows a lot more use for the Plutomancer to actually get out of their appraisal and bartering skills, since they aren't necessarily just selling anymore. They may well be in the market to buy now as well, saving their special currency for more pressing concerns.
Just a thought, but I think it has promise.