How much do we need a membership?

Last night, Amazon announced its first quarter financial report and showed very strong perfoance, especially its Prime program boosted it's revenue. We join different kinds of memberships in the hope of getting discounts when shopping and getting more convenient access it better services, and the sellers use our expectations to sell their memberships to boost their revenues and profits.

The sellers have to make their memberships attractive enough to allow a large amount of their consumers to be willing to pay for memberships, meanwhile the memberships need to be profitable enough. Many memberships make profits based on consumers' overestimation of their commitment. The most normal example is the gym membership. Many people including myself but gym memberships and only go to gym several times in a year. Such behaviour is caused by our overestimation of our commitment to gym and we believe we are going to increase our frequencies of going to gym after we buy gym memberships; however, after we buy the gym memberships, the costs of memberships become a sunk cost that no matter how we behave in the future, this cost will not change at all, so our behaviour is independent of owning a membership after we actually buy the membership.

Therefore, the most rational way to make the decision of whether we need a membership or not is to make calculation about our consuming habit before buying a membership (without a membership), since after buying a membership, our behaviour will not change significantly. However, the problem in the reality is that we do not try or experiment enough before we buy a membetship that we usually buy a gym membership after we attend only one of its taste session. Of course, the sellers do no offer enogh taste sessions and do not have the willingness to offer sufficiently many taste sessions as they want consumers to overestimate their commitment, and this is the way of how they make more profits.