Ha. I'm pretty sure they know what they're doing...

You're confusing an economic impacts analysis (what NERA did) with a cost-benefit analysis. Health and climate benefits are outside the scope of NERA's analysis. And as you say, the coal lobby decided on the benefits on its own. But, an economic impact analysis should include effects on the economy of reduced air pollution (increased labor participation, reduced medical expenditures, etc.), and a huge problem with NERA's analysis is that it ignores these factors.