It gets more expensive to work on a more polished product. If you're only selling like 500 copies for $2 it doesn't matter if the game is janky as hell and crashes sometimes, but if you're selling more copies and want to make translations, ensure more compatibility with more hardware, improve performance, etc that takes more time, and more importantly, it usually means paying people. You also start having to worry about having to do more refunds, marketing, etc. Obviously it can be done where people just keep it small, but it's hard to do especially if the developers quit their day jobs to develop the game. I call this the "Michael Scott Paper Company Problem" where you can end up running out of money while trying to scale up because you are trying to compete on costs at an unsustainable level. Of course, once you get to a large enough scale you can start getting more efficient and can do more to keep your price down, but in this middle range it's kind of difficult.