An expected value system for paying and qualifying audiences (EVSPQ) is an online database system for paying users for their attention provided that they meet a specified condition or conditions. In this system, advertisers post EV payment offers.Using the system, a recipient of EV payment accepts a payment offer; the system stores this acceptance in a recipient's acceptance history, and triggers the execution of an EV payment bet corresponding to the terms of the payment offer. If the recipient wins this payment bet, the EVSPQ enables the recipient to state whether he has met the conditions of the payment offer, and therefore, is owed the payment bet payoff.In an EVSPQ for paying “realbuyers” (EVSPQ-RB) a qualifying condition of payment is that a user makes a purchase after being exposed to a message.The inventive method is a module to be added to an EVSPQ-RB that operates to deter cheating by recipients.The method comprises the following steps: (1) when a recipient claims a payoff from an EV payment bet, the EVSPQ-RB asks the recipient whether he made the required purchase from a seller who has posted an offer in the EVSPQ-RB or from a seller who has not posted an offer in the EVSPQ-RB, (2) the EVSQP-RB stores the recipient's response in the recipients user history, (3) the EVSPQ-RB measures the ratio of purchases from sellers in the EVSPQ and purchases from sellers without, (4) the EVSPQ-RB enables sellers to shield offers from users whose ratio, or equivalently useful statistic, is below a threshold.