The nature of technological progress is that it makes formerly uninhabitable areas inhabitable.
Costs of buses are mostly the driver. Which will go away. The rest is mostly building and maintaining them. Which will be done by robots. The rest is energy. The sun sends more energy to earth in an hour than humans use in a year.
I've done a quick check on the financial statement 2023 of the Amsterdam public transport company, and personnel (which is absolutely not just drivers) is 1/3 of the total.
And use of solar energy is absolutely unrelated to doubling the living areal. That can, and should, be done anyway.
Costs of buses are mostly the driver. Which will go away. The rest is mostly building and maintaining them. Which will be done by robots. The rest is energy. The sun sends more energy to earth in an hour than humans use in a year.