But that's offset by the sheer volume of people who can freely vote. If you have a system where a vote is a payment, you'll likely have a >95% reduction of legitimate voters, and likely a much higher amount of "gamed" voters as a result. Remember, corporations and governments have more money to spend than the average person. I.e. All governments/corporations can afford to spend money + some individuals can spend money. Compare that with: All governments/corporations can freely upvote + all individuals can freely upvote. Requiring money actually skews voting in the wrong direction.
That's why I think Reddit made a smart decision when they implemented Reddit guilding for top-level comments. They did it in such a way that guilding doesn't affect voting, and guilded comments can't even be seen from the homepage--otherwise it would skew the results.
I do totally agree about other ways to support creators, though. I think it's crucial for sites like StackOverflow to implement direct tipping for users' efforts.