The highest quality (both game quality and code quality), best supported game I've ever played, is 100% free to download and play - they survive on cosmetic and convenience microtransactions (as in, extra stash tabs for those of us who hoard in ARPGs, extra character slots for us altoholics). I don't think their financials are public, but I'm sure I'm not the only player who feels guilty for the number of hours I've enjoyed this game compared to the mere dozens of bucks I've spent. The game started out as a far better replacement for Diablo II than the Blizzard one, and they just keep adding freshness and tuning things - and i don't recall a single heavy nerf because they beta test well and are not enslaved by a PvP focus. If you haven't tried Path of Exile yet, do yourself a favor.
Comments, Observations, and Reviews about computer gaming from a looong-time gamer