Only part of the cost of coal is built into our electric bills. Much of the cost is passed on to everyone and the environment, but these external costs are not often quantified. However, an excellent paper by Epstein, et. al., "Full cost accounting for the life cycle of coal" (http://crmw.net/files/Epstein_et_al_Full_cost_accounting_for_life_cycle_...) (2011) does a great job of quantifying those costs.
Their abstract states: "Each stage in the life cycle of coal—extraction, transport, processing, and combustion—generates a waste stream and carries multiple hazards for health and the environment. These costs are external to the coal industry and are thus often considered “externalities.”We estimate that the life cycle effects of coal and the waste stream generated are costing the U.S.. public a third to over one-half of a trillion dollars annually.Many of these so-called externalities are, moreover, cumulative. Accounting for the damages conservatively doubles to triples the price of electricity from coal per kWh generated, making wind, solar, and other forms of nonfossil fuel power generation, along with investments in efficiency and electricity conservation methods, economically competitive. We focus on Appalachia, though coal is mined in other regions of the United States and is burned throughout the world."
At the time the paper was written (2011), coal was the dominant primary fuel for electricity; it is now receding because of competition from renewable energy, effective conservation, and the lowering costs of clean renewable energy, such as wind and solar (and fracked gas, which is similarly underpriced). Although there are significant reserves of coal, much of it cannot be mined or burned due to climate considerations. The paper also covers the idea of carbon capture and sequestration, stating that this technology would actually increase the amount of coal mined and combusted and waste generated by 25 to 40%. As noted in a Politico article, the one plant under construction is billions over budget and years behind in construction. (http://www.politico.com/agenda/story/2015/05/billion-dollar-kemper-clean...)
The paper estimates a low (9.42¢), most-likely (17.84¢), and high (26.89¢) cost per kWh for externalities. This adds to the nominal cost of fossil-fuel (coal) electricity which the US Energy Information Agency estimates are less than 4¢ per kWh. Thus the real cost of coal is several times what electric customers actually pay of coal-fired electricity. If we had to pay these real costs, clean renewable energy and energy conservation would be far more competitive.