A three-year study of about 8,000 gym-membership records from the Boston area found about 80% of gym members with a monthly contract were paying significantly more than if they had gone on a per-use basis.

In the 60’s, Greyhound Bus used to sell a bus-ticket that was good for 99-day unlimited travel for $99 when most round-trip rides cost much less than $99.

In both cases, flat-rate pricing can be profitable when it costs buyers to use as much service as they think they want. Specifically, going to the gym takes time and effort and is more like taking cod-liver oil. It is good for you but not exactly a joy ride. Similarly, few people have enough free time to travel for 99 days although the thought of unlimited travel is very seductive.

Flat-rate pricing is particularly profitable to sellers when its subscription is automatically renewed until canceled. Not only would usage naturally fall short of goal, cancellation also lags behind non-use due to procrastination.

Although flat-rate pricing might benefit those who are using more service than is anticipated by the seller, it might also attract buyers who have been confused by the multi-tiered pricing scheme.

The profitability of all-you-can-eat restaurant boasting of endless variety is always a matter of debate. People tend to eat more when confronted with variety (Nutrition Action Healthletter) and usually expensive items. Red Lobster's Endless Crab promotion in 2003 was so popular that the president of Red Lobster was fired for vastly underestimating how many Alaskan crab legs customers would consume (St. Petersburg Times on line). But there is scale economy in a fixed menu both in the bulk purchasing and preparation of ingredients. There are also high mark-up for side orders not included in the fixed menu. And flat-rate pricing might attract enough customers who have smaller stomachs than their wish to offset the big eaters.