Well, think about it in terms of opportunities.Of course Russia is the only real seller, but I'm afraid that they cannot be trusted to make everything go smoothly. First they will get pressured by the US and Israel not to sell. Then they will put the price up. Even if Iran does get them, Russis is notorious for offering poor after sales support.
Add the fact that the Russians are extremely touchy about transferring technology to even mame a screw, and you have probably the worst people ever to do business with.
Between Russia and China, Russia's offerings are vastly superior in terms of platforms.
Secondly when it comes to after sales support, the benefit of buying a platform like Su-30 is that there is an international supply chain (that is apart from Russia) available. Which means that there are other players in the market from which close to everything of a Su-30 can be bought.
That means there is India and China. China produces an older version of Su-30 and India produces the modern Su-30. But both make almost everything.
That means that if Russia dawdles, there are other suppliers that can take up the slack. And both India and China are independent players with our independent foreign policy in the global arena - as shown when both defied international sanctions against Iran.
Which means the situation what happened with your F-14's will never happen again.
Also, if Iran buys ToT then it would be a boon for us as well. It increases international availability of parts for us as well and possibly drives down international costs.