Lots of single girl sites charge more than $19.99 per month. Personally I think anything more than that is a lot, yet lots of people will pay way more, so it's probably not an issue. And I like to promote sites that charge a lot, so that I get a bigger cut
I just say charge a fair price for what you think your site is worth.
But yeah, if you get a better password protection in place (including using a form login), you won't have to worry about bandwidth theft/stolen passwords as much.