Seriously though, (don't take this personally, but) being concerned about the hosting fees is probably one of the single worst reasons I've heard to NOT launch something. As mentioned, there are HUGE swaths of services which will host you for less than a dollar a month. Clearly, you won't be relying on them to give you five 9's of uptime but will certainly give you enough of an indication if your product satisfied enough paying customers to make it worth your while.

Hell, if you want, I will put you up on my reseller server and not charge you a red cent until you hit your 100th paying customer. And I'll even help you migrate to better hosting when you're ready. No, you won't get 24/7 technical support, but you'll get a control panel to handle 95% of what you'll need. Let me know if you're interested.

Anyway, yes. If you feel like this is something you want to invest more time into and want to offer it to the market, then by all means give it go. Worst case scenario, you'll experience the sweet stench of failure. (At which point you'll dust yourself off and try again.) :D