My gut reaction is a worry that because people in general tend to upvote things they already know and agree with, giving extra value to upvotes might create even more bias toward boring conformity. I imagine it would deter users with different interests or opinions from participating, since they wouldn't want to spend money just to risk being ignored or shown the door.
I think successful communities fight such stagnation by being focused and moderated; people join because they care about the topic the community discusses rather than the people in it, and trust moderators to trim upvote-farming relatable memes, over-discussed subjects, and interpersonal drama, to keep the spotlight on topical discussion. Anything else tends to lead to 4chan /b/.