The main reason that people aren't donating money to the game is that it doesn't worth it.
You are donating 10$ or more to the game (which could be a lot to some people with paypal) and you're only getting a game-title next to your name on the scoreboard, which doesn't really worth it.
I think that donators could get more than that, then, when there will be to the Donators more features, people will understand that donating to the game pays.
Some examples for the features:
-People that you were killed will turn to silver or platinum. (Similar to the beta testers)
-Special color for what that you're writing in chat. (Like gold)
-Chat title and not only game-title on the scoreboard (next to your name in chat there will be the title: [Supporter])
Those features will make donators to become more specials.
If you dont agree with my suggestion because you think it buffs donators or from other reasons then:
I suggest to be able to donate less and still get that game-title because lets be honest, as I wrote, it doesn't really worth to donate 10$ for that, maybe 5$ if you really love the game and want to help it.