If that really is the case, I think Congress has the power to require them to consider costs. This is exactly the kind of BS that goes on in DC that people want fixed, and in one big hurry.
I don't think there are words of sufficiently few syllables to explain it to them that they can be made to understand.
That is the case and has been the case for a long time. This has been argued before the courts numerous times.
The cost benefit analysis is done at the state level. EPA sets the standards and the states determine how to meet the standards.
A good example is playing out in Texas right now. The lege just passed the bill on nat gas as motor fuel. This is being paid for with money from a fund that had been set up to reduce emissions from off road construction equipment. Somebody did a cost benefit analysis and found that shifting the money would reduce more emissions per dollar.