Android app for Cloathes Store Catalog

We need to develop for one client an app to show his products. This is our very working with app, them we really don't know the necessary budget to do it. He have one clothes store, and we need to make an application to his sellers use as an toll to show the products etc. NOTE: WE REALLY NEED ONE SOLUTION TO ADD IT AS AN APP, WE CAN DO EVEN IN HTML RESPONSIVE, BUT WE NEED IT TO BE INSTALLED AS AN APP ON USERS ANDROID) We gonna provide all design for the work (PSD's), and we need the price for convert it to an app that can be installed on anyones Android. We going to to this app to iPhone also, if you have one solution for both, please make bid for both.