Hey there,
I am a highly experienced software developer, with over 12 years of experience and excellent English communication skills.
I have dealt with developing complex web solutions, and have a team who can manage developing such solutions, along developing mobile applications (android and iOS)
In terms of your project, you do have a complex project at hand. And you requiring both an Android and iOS version as well will definitely increase your cost.
Basically, for such a functionality for an online store, you could be looking at around 6 months of development. What we normally do is setup all the database layer essentially, and work in parallel on web, android, and iOS versions.
Roughly speaking, very roughly, such a project would cost nothing short of $10,000 USD, getting quality work of course.
after further consideration of requirements, we can provide a more detailed estimate and valued cost.
Feel free to contact me further via email through mcfarhat AT gmail DOT com
Cheers