I believe xbryanx was referring to the externalities (ie the costs arising from pollution, global warming, etc that traditionally go unpaid by the producer) rather than just the financial cost of producing the power.
Perhaps. But you don't hear about those things with the green power alternatives, either. Like, for instance, the pollutants created when manufacturing solar panels, or the amount of energy consumed in making them and safely disposing of them every 15 years or so. I'm not going to cite any articles here, because at my knowledge level, it's near impossible to separate the biased articles on topics like this. But a simple search for "pollutants from making solar panels" will garner some things to read about it.
I suppose I should say at this point that I'm all for green, cleaner energy, and wouldn't go so far as to say I'm "pro coal". I do, however, think that living in Michigan (which is lucky to have a single sunny day a week) makes me a tad pessimistic about using solar to power my house. I'm well aware that it makes more sense in places that can practically guarantee sunny days 6/7 days a week, but the TCO will need to improve massively for it to make sense in my region.
That doesn't factor in numerous externalities such as healthcare costs due to emphysema and other diseases caused by coal smoke, ocean acidification killing fisheries, rising sea levels displacing seaside residents...
That depends on how you define "sustainable". So far, a perhaps pessimistic assessment of sustainable energy is that it's driving up energy costs, while reducing the increase of CO2 emissions by only a very small amount. It's increasing fuel poverty and deaths from cold weather events, and ultimately it will drive business out of the countries that are building sustainable energy into countries that have cheap energy, by making business uncompetitive. Then, people will buy products from the cheap energy countries that are emitting CO2 (although they'll be poorer, so perhaps they'll buy less).
It looks to me that coal is one of the cheapest forms of generating electricity there currently is. [1]
[1]: http://en.openei.org/apps/TCDB/