You are confusing cost of acquiring a car with cost of ownership, because the graph you posted actually shows that running costs in London are one of the highest in Europe (light blue bars), even despite the fact the graph averages all capitals by using the same mileages, whereas we do more commuter miles in UK than many European counties, therefore we do pay even more due to higher distances travelled on top of overall higher cost per mile.
The only incentive people need to use public transport is for it to present at all and be affordable. End of. First hand experience. I live 36 miles by nearest train from my work place. 44 miles by car. The HS1 train with underground travel card costs £45.10 a day plus £5.70 to park by the station. Journey by car costs me £16 in fuel door to door. Not because motoring is cheap, but because public transport is insanely overpriced.
So of course I commute by car. I don't want to do it, but I have to do it. I will not leave extra £700 a month to pubic transport to travel to London with few changeovers on the way, just because they lost touch with reality.
Now, with prices of public transport this high, I can't imagine any young person in my town ever starting work in capital just 36 miles away, simply because if they were to earn national minimum wage at the start of their career they would have literally couple of quid left in their pocket after paying weekly travel costs.