You've got APD to thank for that. £26 for every return flight. BRS has viable alternatives and it's shrunk considerably. STN ahead viable alternatives and has gone from four daily to zero. BFS doesn't have a viable alternative. People don't want to spend hours on a ferry, then a rickety old expensive train. So there is a fare premium that people will happily pay for the BFS run. BRS/STN are very different.