1. A computer implemented method for purchasing a product comprising: using a processor in a system including at least one subsystem having a computing device with the processor and memory for storing executable instructions that are executable by the processor to perform: comparing, with the processor, price information of products determined to be similar, at least one of said products' price and product identification having been electronically read off of a display screen via an optical scanner of a mobile device and communicated from the mobile device; selecting, with the processor, a product that is simultaneously offered for sale and based upon whether the product's price falls within a predetermined price difference percentage range compared to the price of the product simultaneously offered for sale whose price and product identification were electronically read by and communicated from the mobile device and based upon whether the product whose price falls within the range of price difference is available immediately or is on back-order and based upon a distance between a current location of the mobile device and the product; and automatically placing a purchase, with the processor, communicated from the mobile device for the selected product based upon a calculation including factors of least cost and least time to obtain the product performed using a comparison of the product prices falling within the predetermined price difference percentage range, the product availability, and the distance between the current location of the mobile device and the product, wherein the least cost includes an estimated shipping cost or an estimated gas usage cost that is based on the distance between the current location of the mobile device and the selected product, and wherein the least time includes a time to travel the distance between the current location of the mobile device and the selected product and a time to receive the product based on whether the product is available immediately or is on back-order.