The cost analysis is done exactly how any corporation would do it. If you want externalised costs to be included then it has to be done by government policy.
And good luck getting re elected if such a policy has a noticeable impact on people's lives.
This is precisely why policies such as carbon credits are required, otherwise doing things the "dirty" way is too cheap for the "clean" way to be competitive.
Socialise losses, privatise profits is unfortunately the current norm.
And good luck getting re elected if such a policy has a noticeable impact on people's lives.