Regardless of how much of an additional tip a voter decides to give to a poster, the voter would have to vote N times to move the score by N points. This becomes less economical as the overall user base grows. But more generally, I think that money already plays a huge role in deciding what is worth discussing. From promoting a blog post on Facebook to lobbying, we see this kind of influence across media throughout society.
On one hand, reputation matters on Hacker News because of the high-value culture maintained by users and administrators. But this doesn't scale past a certain size, and reputation becomes something that not everyone can earn or buy on equal terms. Consider celebrity accounts on Twitter bootstrapped with fake followers or karma farming and vote manipulation on Reddit.
On the other hand, I think one way to look at this project is as a micro-crowdfunding platform for interesting ideas with curation serving as a form of gamification or competition.
While I think that being explicit with money might have an interesting effect on what content gets surfaced, it might also be interesting to maintain a subreddit with mirrored content to compare the results.