Thanks to commenter "G N" for doing my legwork for me. Here is a link to an RIA supplement from the EPA where they say that annual benefits and costs in 2020 of the delayed smog rule range are as follows.

For the .06 ppm standard:

- Benefits range from $13 to $37 billion
- Costs range from $19 to $25 billion

For the .07 ppm standard:

- Benefits range from $35 to $100 billion
- Costs range from $52 to $90 billion

Since a central tendancy of the range is not given*, taking the midpoints as the best estimate generates annual net benefit (in 2020) estimates of $3 billion and -$3.5 billion for the .06 and .07 ppm standards.The best case net benefits are $18 and $48 billion for the .06 and .07 ppm standards. The worst case net benefits are -$12 and -$55 for the .06 and .07 ppm standards.

The delay in implementation of the rule looks like a good idea from an efficiency view.

*Doing my own legwork, more estimates are here on page S1-4.