I am an account exec at a web and mobile development company and hear this question everyday. Unfortunately, iPhone apps are not cheap. You can expect around $100 per hour if you are staying on US soil. I have seen some offshore Indian developers out there for as low as $20 per hour. It all depends on the number and complexity of the functions you wish the app to perform. Simple one function apps are normally around 4-5k. They are so expensive because you are paying a team of people a healthy hourly wage and any type of raw prototyping, development, and coding takes time. Apps can exceed 60-100k pretty easily. Southwest Airlines making an app with a full ecommerce platform that allows you to buy tickets over your phone is an example. All of that porting into their IT is a big job.
And offshoring the project is definitely not always a better option. If you do so you better know who you are dealing with. Do not get me wrong there folks over there who do a bad ass job for a way better deal, but they are not that easy to find. Those guys could fuck around for 5 months on a simple project that would take 6 weeks here, or just not complete it at all and hand it over half finished. I have seen this scenario many times where we finish the work. The project management becomes a challenge. It can be difficult to communicate exactly what you want the app to do.