I agree that $100 is pretty steep to pay for the possiblity to maybe get your game on Steam. It's good at least that it's a one time fee, but $50 would have been more reasonable.
At least the money is going to charity.
I don't think the downvote is necessary. If it doesn't impact the votes, why call it downvote at all? IMO they should just change it to "Ignore".
More like "Hii, i am steam, if you want to publish your projects on Greenlight, you must pay $ 100 one-time, because there are trolls can't afford $ 100 to submit their fake projects, your $ 100 goes to Child's Play. (Hehehe i take $ 99, and $ 1 goes to Child's Play)"