Iphone Photo Sharing App

We are looking for an experienced iOS developer to build an iPhone app similar to most of the photo sharing apps already on the appstore: picyou, instagram, hipster, etc. Some of the basic features would include registration, pick a username, upload a photo from the camera roll and take photos, tag and comment, flagging, and push notifications, browsing photos and sharing to twitter and facebook. The ideal candidate would be able to do both client and backend/server work. I would like to have both a time and cost estimate for the entire project. Must have the following experience: Extensive experience building iphone apps Facebook and Twitter api - Users must sign in/login with facebook or twitter or can sign up via email and password. User will be able to pick a username. Amazon S3 - Photos will be stored here PHP and Mysql - Database will be created in mysql and server side will be php I already have the final design assets for both 3g and retina display.