I disagree with your opinion but I want to explain why.
If someone is going for the cash prize.. nothing stops them to just vote all of the other games with a 1 in every category even tho they can't vote for their own... or even worse don't vote at all? That means that the results would not be "honest" anyway.
Or what would happen if someone would make friends join the jam just for the voting even tho they're not going to actually submit or they submit some piece of trash?
I have already seen this happen in jams with no money at stake so...
When money is at stake the only "above the parts" opinion is the one of the guy (guys) putting the money in because it's in his(their) best interest to give those money to who deserves it since they're putting those in.