This is actually an easy problem to solve: define a list of extras in the standard including fees. The structure for each extra can be pretty rigid. Something l

This is actually an easy problem to solve: define a list of extras in the standard including fees. The structure for each extra can be pretty rigid. Something like e.g. short-name: Tray fee long-name: You get a foldable tray for seat to use during the flight. price: 39,99 includes-tax: false This is basic data modeling, really. Tne real thing would probably have closer to 50 well defined fields instead of 4 because of real-world self-inflicted complexity in the system, but the concept is the same.