OK, so the economic argument has to be some form of, 'Investing in renewables (solar, wind, geothermal) replaces an efficient/desirable/optimal form of energy (coal) with a less efficient/desirable/optimal form of energy, and that coal alternative is projected to remain less efficient for the foreseeable future." Or, a simpler way of phrasing the question is, all things considered, how do we want to produce energy in 20 or 30 years? Do we want far more of our electricity to come from solar/wind etc. or coal produced by lopping off the tops of mountains that when burned produces a mountain of toxic waste?
If we reduce that to purely economic terms, then you'd estimate the cost by source (i.e. coal, solar, wind, nuclear, natural gas) look at some discounted cost of electricity produced over 10 years for each method. But the problem is that cost figure has to be complete. If I can produce electricity at $80/unit, and solar costs $100/unit, but to get to my $80 I ignore that I kill a bunch of people and make MANY others sick, but because my method only does these things directly, I bear zero cost for those harms, then the comparison is a false one.
Just for example, the coal ash retention pond (i.e. toxic waste dump) at a TVA coal fired plant near me in Kingston failed a few years ago, and dumped millions of tons of waste into the lake and surrounding land. Now they're finding that the workers who cleaned up that mess are suffering from all kinds of serious illness because they didn't wear protective gear while cleaning up sludge loaded with toxic chemicals including arsenic. Well, the cost per unit of electricity at that plant HAS to include all the costs of that spill, including the future health costs of those who got sick cleaning up the toxic waste. It would be nice for TVA and coal advocates to not study those who got sick, trace it back to the cleanup, link the correlation with the causation, and then fine the ever loving crap out of TVA sufficient to cover the health costs of those sickened from the cleanup for life.
The TL/DR point is the studies are essential to, at a minimum, assigning a true cost to mining and burning coal. If we don't do them, it's just a way for coal companies to understate the cost of coal, and, relatedly, to offload those costs onto the rest of us.