http://www.carbontracker.org/in-the-media/phasing-out-coal-p...
The issue is that they're mostly escaping market forces due to how they are regulated:
"“Merchant” coal owners operating in competitive wholesale markets have lost nearly half their value in the last two years amid fierce competition from cheap gas and renewables. However, two thirds of coal plants are “regulated” and receive government-approved prices which cover their costs. This means that consumers rather than shareholders pick up the bill for supporting uneconomic coal plants."
Once you start counting actual externalities you get numbers like $5 Trillion a year subsides for fossil fuels globally, as estimated by the IMF, 7% of global GDP:
http://www.imf.org/en/News/Articles/2015/09/28/04/53/sonew07...