Well... yes? Like, first off, we all know what 100 dollars in labor is like. That doesn't mean 100 dollars in labor is AVAILABLE. It doesn't mean that they aren't already working as much as they can. And again, this isn't to say that a lot of these people COULDN'T afford it, but is disproportionately burdensome to them, all for the right to be part of a janky popularity contest.
And AGAIN this isn't Valve setting up a business model or something. This isn't your usual cost of doing business This is Valve saying "Prove you're serious. Burn a hundred dollar bill right now. We wanna see you financially hurt your self to prove how serious you are". Also the benefits of having the value as high as it is... is .. dubious at best. To take this in a ridiculous, implausible turn, would it be fair to ask submitters to cut themselves to prove their seriousness? It certainly would cut down on worthless entries, and anyone who was serious about their game would probably suck it up and do it, but I think we'd al lbe wondering "WTF does a willingness to cut your self have to do with my game?"
I don't think Valve is being purposefully discriminatory, nor do I think derogatorily calling them "gate keepers" is far (I mean, they are, but they're the gate keeper for their own home, and they do not monopolize the PC platform), but criticizing the situation for the lot of us who see this as less than ideal is important.
So it's not about this barrier being insurmountable. Like Mongrel said, it's a relatively low one, all things considered. But it's also an arbitrary one -- no one's getting a slice of the pie to provide you services or something. It, to me, just feels really gross right now. People already are finding ways to get over it (there is a whole website for people to sponsor games and stuff), but is that really how the system should work?