Yeah, one thing I need to do is to make sure that the people who are coming in for free are not just lurking around. They are not heavy consumers of the service, but the idea is that the first ones should come to help bootstrap the instance content.
As for what you are doing for your minecraft server, I think it is quite reasonable if you treat it as a hobby. You are not doing it expecting compensation, so at least you should be doing it in a way that you can be healthy and sustainable.