It seems to me like the kind of thing where a 30 day free trial followed by a small monthly fee ($5? I don't know, something in that ballpark perhaps) might wor

It seems to me like the kind of thing where a 30 day free trial followed by a small monthly fee ($5? I don't know, something in that ballpark perhaps) might work - if people enjoy using it and become dependent on it during the trial, at least a portion of them will be okay with paying afterwards.