The context of this question is a small web design company that wants to branch out to do mobile application development. I am wondering two things:
Mike Lee famously raised his rate to $1,000 per hour for iPhone apps. That's a pricing anomaly, of course, but the consensus seems to be that rates for freelance mobile developers in the U.S. range from $100 to $150 per hour.
I would say that obtaining even those rates is dependent on a host of factors:
The old maxim of "desired salary divided by 1000" might help you in setting your rates. That is, if you could earn $80,000 as a permanent employee, expect to charge at least $80 per hour as a freelancer just to stay at the same level.
It's impossible to estimate project costs without knowing the client's requirements, but another old maxim of "double what you expect" might be helpful. As you're new to mobile development, I would encourage you to factor learning time into your estimate, unless you're willing to eat that portion of your time.