471392 Iphone app development

I have a concept for an iphone app. I need someone who has experience developing apps and submitting them to apple. Please show existing apps that you have created. This app will be very simple. It will require user accounts. The user will be able to submit an item and provide title and description of each item. This will also require location services from the iphone. Please provide development cost as close as possible...a ballpark figure. Im a graphic designer / web designer so I can provide mock-ups for the interface...and graphics assets.