1. A computer program, embodied on a non-transitory computer readable medium, the computer program causes the processor to provide offers and receive acceptances in real time to effect a transaction regarding an item constituting a good or a service between prospective customers utilizing a point-of-sale (POS) terminal, the processor is further configured to: establish communication via the Internet between an upsell system and the POS terminal for purpose of a primary transaction comprising an Internet purchase transaction; obtain primary transaction data at the POS terminal with respect to the transaction, including the identity of the prospective customer; obtain at least a second data element representing at least one of the user's previous purchases and the user's responses to survey questions at the at least one of the upsell system and the POS terminal; calculate a current demand parameter based on previously conducted transaction times measured over a predetermined period of time that represents a level of demand for primary transactions with the POS terminal, the current demand parameter representing a value indicating that upsell items may be offered to the user without increasing the average transaction time required for a user to complete a transaction on the POS terminal; determine whether to perform at least one of offer an upsell item and suspend the offering of an upsell item to the user based on the current demand parameter; analyze the current demand parameter, the primary transaction data and the second data element in the upsell system in determining at least one good or service item for prospective upsell to the prospective customer; display from the upsell system via the Internet an image of the item to the prospective customer in real time; and receive an acceptance of the offer from the prospective customer to consummate the transaction.