Railways have an even lower marginal cost than planes. DB would rather have a person travelling in the seat for 'free' and encourage ridership than have it empt

Railways have an even lower marginal cost than planes. DB would rather have a person travelling in the seat for 'free' and encourage ridership than have it empty. Airlines used to think this way - the marginal fuel cost for a seat was something like $10 (essentially it only costs you at takeoff). But then airport improvement fees, security fees, faa upgrade fees meant that they were paying out $100s for passengers who were travelling for free.