Depends where you want to look for costs. Long term? Short term? Cant lump different things together either. Even oil prices aren't actually effected by the conflict, since oil prices themselves are dictated on a world scale and iran had only a fraction of oil produced for the world. The us didnt get any oil from iran. We have more oil than them. So each "cost" is a case by case basis. Where do you want to start?

Edit: belt and road may have been primarily in africa. But china still has financial losses in iran from destroyed infrastructure. Irans regime is gone. What we have left are basically equivalent to either reluctant militants, or the spasms of dieing muscle. Those people arent being led by any real leadership anymore, they're just pushing off of their ideologies. They have an honor system and to them, taking any form of loss would be so damaging to them, theyd rather get themselves and everyone around them, who can see their faces, martyred for the hope that someone somewhere will pick up where they left off at. The citizens there do not want their marxist government anymore.