That price will depend on whether they use a carbon tax, cap and trade, or both. Still very fuzzy and hard to nail down. It could get very expensive to not comply and reduce emissions. Carbon Tax might just be a small part of the cost.
If EPA sets hard emission limits (and they seem to be doing that already), that is a whole new ball game called MACT and BACT, Maximum Achievable or Best Achievable Control Technology! And EPA does not need Congressional approval to nail the CO2 emissions sources hard now, because they have a federal court mandate and Obama in office!!!! :-)