Theoretical cost of a Vanilla based iOS app with HTML/CSS/JS wrapped with PhoneGap

Since I'm no programmer, and since a lot of you are, I'm asking this here. I'm outsourcing a project on vWorker, and I've received bids and communicated with some candidates, and I want to get some idea from non-bidders how much this project really would cost to make (they're offering to do it for $1000US).

It's a server running Vanilla, and an iOS PhoneGap-wrapped app that communicates with that server. There are minimal features, just the absolute basic functionality of Vanilla, with Facebook integration. There's only one forum/category, and all the threads are in it. The two custom features that I want are two placeholder functions (I will write them in PHP later), and they are: a function that determines whether or not a thread is open for posting to a given user at any given time, and a function that determines which posts in any given thread are partially hidden (some posts will be fully visible, just like in any standard thread, but some have their content, the part that the user wrote, shaded out/hidden).

My worker said that it will take significant AJAX scripting in PhoneGap to get this to work, hence the $1000. How right is he? How hard is this project really? Everything needs to look and feel native, so I suggested using jQuery. And even with that, it's still at $1000.

Any help/comments/thoughts will be appreciated. Also, "Forum/Thread/Post System with iOS mobile client" is the title of my vWorker project, if anyone needs more information.

Thanks good people.