I make over $1000 a month, but less than $5000 a month (on an average month, not including months with updates) from my two main iPhone apps: Color Stream (http://colorstreamapp.com/) and Dayta (http://daytaapp.com).
Thanks for being open and sharing this. I agree with the author of this article that more openness with regards to sales people are getting as iOS developers is only a good thing. If people had more open discussions about this sort of thing, perhaps it will quell some fears newcomers may have before joining the Apple dev program.