Write an iphone app which is already available as an Android

We have an Android App that is already available on Google Play and want to get an idea of pricing to get it recoded for iPhone and perhaps for access via iPad/tablet/or even computer? We will proceed as quickly as we can afford to so cost is important in determining timeframe as we will budget accordingly.
In the longer term we want to add functionality and perhaps a social chatting facility. The current app has an in-app purchase facility that sends data to generate a personalised report from the information that people put into working through the App. This is generated by a third party data processing house and works fine so would need to create that interface from the App store as well as from google play