there are lots of FBA apps that will let you scan a bar code and tell you how much it is selling for on Amazon, and will factor in Amazon's commission, shipping

there are lots of FBA apps that will let you scan a bar code and tell you how much it is selling for on Amazon, and will factor in Amazon's commission, shipping costs, etc and will tell you the absolute max you can pay for an item and still make X% money off of it.