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Games can also sell a lot more than they did in the days when fewer people had computers and online distribution wasn't a thing. The more copies you sell and the lower the cost of distribution, the lower you can afford to make your price and still make a profit. There's also a lot more games, and thus competition, in the market and price is one way to convince people to spend their money on your game instead of someone else's.
As was pointed out, this is a multiplayer-only game so the player population is paramount to its success. Plenty of excellent multiplayer games (Section 8: Prejudice comes to mind, which is also $15 by the way) have withered on the vine because they never pulled in decent player numbers. Whether $10 would actually be the magic number or not, I don't know (I don't have access to their sales numbers, obviously), but it's not an unreasonable number at the least.
Uh...it's not even close, assuming they meant F2P and not freeware. Not that I think this game needs it or anything, but F2P is a perfectly valid business model that can make developers money. I mean, we've even got MechWarrior Online and Hawken as two examples of F2P mech combat games.