I guess the fossil fuel infrastructure is actually more expensive? (Drilling, refining, shipping of the fuel: all not needed for wind and solar.) But this infrastructure has already been built and paid for, and now someone with a lot of money wants a return on their investment over the next 25 years. Which is not going to happen in a world where we prevent the worst climate change.

(Also, investment to decarbonize things like cement are not going to happen if fossils stay cheap.)