The cost per MW is surprisingly comparable, with combined cycle gas-fired plants rivaling many coal-fired plants. I don't watch the daily costs, but what I've seen more recently, the most efficient coal-fired generating units still run at a lower cost than combined cycle gas generation, but not much lower. And a lot of smaller, older coal generators are more expensive to run than gas.
The big disadvantage for coal right now is one created by the government - EPA standards have become more stringent and are being applied to older units. Utilities are finding that it isn't cost-effective to retrofit older generation with the latest pollution control equipment and are closing down many of the older coal-fired generation instead.
It's not because the plants are no longer servicable, it's because the EPA has grossly overstepped its authority.