You're totally missing the point. Very obviously Piloting an aircraft and managing a crew requires a much higher level of skill than driving a tube train.
Unfortunately in the UK that will not justify higher salaries for two reasons:
1. Unconstrained training of new Pilots meaning a flood of young Pilots coming to the market (It is a market). From next year, those young British Pilots will be limited to a UK job. British Pilots do form the majority of Pilots on a per country basis in the EU.
Even amongst US part 121 Airlines a 4 year degree is generally required to be a Pilot.
2. No strong Pilot Unions.
If I started an Airline right now in the UK and offered £30,000 per year for an experienced Captain, I would be overwhelmed with applications. Mostly from middle East and Asia returnees. These people are high quality though. Their safety records are not lower than BA.