If you believe Russia had any economic sanctions in place against Iran, there's a bridge in Brooklyn going cheap... I'm sure the Russians want to sell a truckload of weaponry to Iran, including nukes, but if Iran detonates a nuke on American soil, the return to sender address will point to Moscow. Does Russia really want to be irradiated for a few billion dollars? Besides, Iran's not exactly flush with foreign exchange, given its communist economic structure. (Yup - it's Islamist in the social realm, communist in the economic realm - the best of both worlds, from an asylum inmate's point of view).
The same problem exists now as before, we irradiate Moscow, they irradiate us. They still have nukes too. But you forget the threat of Western sanctions will require retaliation. All the hawks calling for blood had better think twice before continuing this America is the policeman of the world crap. Keeping in mind part of the 17 trillion deficit can be directly billed to that idea, economic collapse is just as big, if not a bigger threat, as any war.