If price discriminating on board still doesn't satisfy you, you can also price discriminate based on route. People will pay more to travel between certain cities, so you can charge more for those cities.

So much so that I can fly direct from San Francisco to Detroit for around $500, and fly indirect from San Francisco to Cincinnati, stopping in Detroit first, for around $150. You can find these “hidden-city fares” on Skiplagged, though you risk losing checked-in baggage and getting banned from airlines.