I'm thinking that a list of prices might well be way over the top unless they are tied to GPS location, and then it might still be too much. Also, I think that it is highly likely that the price will have to be adjusted manually in most cases anyway because of constant fluctuations, sales, etc. Maybe furnishing the prices could be optional??
For me, the most useful functions will be the option to add a new item or attach to a pre-existing item and the ability to have the app prefill all the other pertinent info . . . brand, package size, unit type, and whatever else can be gleaned from a barcode.