>Coal is cheap

No it's not. I'm not talking about the environment either, coal plants are just straight-up more expensive than gas plants and renewables.

Coal plants are necessarily steam turbines and not internal combustion, because coal is filthy and the mercury/sulfur/etc would wreck the guts of any machinery it goes through. Thus, it's only used to boil water.

Gas turbines don't have that problem, so they spin the turbine with the combustion products directly. They're far more efficient, the machines are smaller and cheaper, and because you don't need to wait for a giant kettle to boil before ramping up the power, they're far more flexible and responsive to demand. It also helps that the gas is fed with a gas pipe, whereas coal needs to be fed with a bobcat.

Which is why nobody is building new coal plants - they're way more expensive than gas plants, even if the gas fuel itself is more expensive than coal.