@rampant yes this could be very easily done with great results. I think initially they wanted the money to be seen so as to attract people by the idea of making that money. Yet instead what is happening is people are seeing the big $$$ and getting excited and realizing it's not likely they will make any and get frustrated and leave.
It is also as said that when a voter sees their vote not increase the post value at all they feel worthless.
While hiding the $ amount wouldn't change the value it would help people feel like their vote was more meaningful.