Hi,
We're very glad to see your project, we believe you're very serious about it. First of all, we want you to know that we read the description very carefully, and there is no obstacle for us to finish this job. We're confident we can to deliver the best result.
We bid with much higher price than other developers and we think it's still very reasonable price. You want to develop the app in 2 separate mobile OS (Android and iOS), so the price should not be less than 2000$. Anyone who bid with lower price is not really serious about your job. We have experience in this field so we understand how to give reasonable estimation (both time and cost). I don't want our client spend money for nothing.
We really love to work on this kind of app also. We don't simply finish the job and take money, this is our job and the result shows what we have, what our value is. We will work with passion and the desire to create a good result for our client. We will help you to fix if there is any issue comes after delivering it for you.
Finally, we suggest you to go with iOS version first, because we often have changes while developing app. After you satisfy with iOS version, we can clone it to Android very quickly.
Please consider about everything and let me know your response.
Thank you very much!