I'm still waiting for my first dollar from my password generating android app "Password Specialist". It was added in Dec 2010 to the market and still 0 sales :)
hate to be a stick in the mud, but aren't passwords hard enough to remember when they're not randomly generated?
Don't give up. Make a free version that only generates 3-5 passwords. No one will buy just based on the screenshots... everyone wants to try something out first. That's what I did for my android app, and now I get a few sales a day.
I would suggest you keep at it. Iterate, iterate, iterate