In the real world pricing is set by response to competition, and a desire to sell at the price that delivers the best overall yield. That may mean a higher price and a lower volume, it may mean a lower price and a higher volume, or a low price on one item that triggers the purchase of other highly profitable items. Effect on labor and handling costs are factored in. Also, food service can be used as a tool to attract passengers at a higher price point than if it wasn't there (DownEaster is a perfect example of that concept) Lots of people complain that the beer is expensive at MSG or CitiField, but they sure buy a boatload of it. Unless you are running a social action group or a charity, why would you price under what delivers the best points on a yield curve for the route (which factors in effect on passenger loads and price sensitivity of fare points)?