At £9.99 you are sustaining nothing. You are simply burning cash in the hope that your opponent blinks first. The ultimate prize being to knock them off the route at which point you can charge what you like. It’s unsustainable in the long term but they’re be a few thousand passengers who benefit. Unfortunately they become that familiar breed that believe they should be able to go where they want, when they want for £20 and cry about it when reality bites.