Price discrimination

Why does a cheap airline ticket become expensive by the time you pay?

Airlines increasingly separate the seat from services that were once more often bundled into the fare. The low base fare is easy to compare and attracts attention, while baggage, seat choice, priority and flexibility depend on what each traveller adds. Unbundling can give light travellers a genuinely lower price, but it can also make the final cost harder to compare at the moment when the headline fare is doing the most work.