Cost Analysis For Retail Scanning System.?

I’m trying to get an idea on prices for a semester long class assignment. The idea is to develop a hypothetical system for a retail store. Customer would grab a hand held scanner, scan the items they want and put them in their cart. At the checkout they’d place the hand held in a dock and the system would give them their price and the customer of course would pay and leave. This is all to be accomplished with little or no workers in the store, including security personel. The best I can come up with is to have an RFID chip on everything and when the item is scanned the code would be sent to a database via wifi. At check out, after payment has been accepted by the clearing house, all the scanned codes would be transferred to the security scanners at the front door so that when the RFID reader encounters these codes and “sees” they have been paid for…etc, etc. So two questions. 1. Am I even close to being on the right track? 2. I have no idea how to come up with prices. I have found various scanners that could someday be implemented, and there is also a company that claims in the near future there will be silicone based RFID tags that might be as cheap as 5 cents a piece. However a lot of the other stuff is outside any frame of reference I have. Such as what kind of computer system do places like Walmart already have and how much does it cost? Is it Unix? How much would a programmer get paid to enter all these bar codes into that system. How much is the Wifi feature etc. etc. I really don’t know where to begin and Google hasn’t been much help believe it or not.