Yes, it does cost money to host a server, but that doesn't mean you get to go around taking extra money for nothing.
You should just do what CipSoft does. When you need money to pay for your monthly (or whatever) host, just do a little promotion.
For everyone that donates at least 5 dollars, gets a free mount or something, then end the promotion when you get enough.
When you need money for host again or something, just do another promotion.