I think there is a big difference between a business paying an iOS developer $100-200 an hour to make an app and a software developer releasing an app in their spare time. I'm in the process of doing the latter. I've got an idea for an app which I believe is new and original and I hope I make more than $100 a month. Really, I'm hoping for 1000 sales a month in the first few months but that might be overly optimistic.

I'd be fine with $100 a month though. Really, as long as I make $100-200 overall I will recoup my original investment and have learned a valuable professional skill.

I think marketing is going to be a problem. Becoming lost in the appstore seems like it could be an issue.