Hi MissMuck,
While seemingly simple, getting the book App to look good on both the iPad and iPhone, which have different resolutions and versions, means considerable testing. Apple also refuses apps for very small details so timing can be difficult to specify precisely. Unlike the eBook conversion, the App is more like a software development project. My App man reckons the devil is in the detail with jobs like this. That is why I have bid above your budget. Cheers Ben