Before I get too involved in looking at how to build something, does anyone have a rough idea on what it costs to have an app built for on-line sales ?

It's a small catalogue, less than a dozen items but maybe more in the future. It will need to handle returning customers and CC payments, send email/text confirmations of order receipt and completion details and be as simple to step through as possible. For both Android and Apple. I'm looking for simple rather than jazzy.

Just a rough estimate would be great. Very few websites I've found give any indication at all, although one started at $5k for a basic app.

My gut feeling is to just do a website and keep it as minimal as possible, but I've not built a mobile app before ;)