First off, that page could be outdated and could be incorrect. However, they seem to have done the calculations and seem to think that the game is sustainable on this budget.
Personally, I think since it's such a small game maybe they can keep it up with a very small budget. Or they can take donations. Some games, such as the graphically simple but incredibly complex Dwarf Fortress, survive only on donations.
Bottom line, whatever the team (or single developer) decides to do, they need to get more players. Just charging more is a rather silly way to try and keep the project running. The only other option would be the devs funding the game themselves, and while that's always been something I've personally approved of (and done), I don't think they'll do it themselves.