Skipness
I don't think we should nationalise heathrow, but I don't think we should subsidise it to the level it seems to require to expand.
The £18 billion is from TFL, and covers surface access schemes likely to be needed to alleviate increased demand to the airport.
As Bagso says, the argument is about who should pay for it, not whether it should happen. Whatever sum it is (and I don't want to get into an argument about a billion here or there) it is a huge sum of money.