The Israelis have suffered no losses in taking them out and we’re even better equipped to do so than they are.

The “cost” would be letting them know we can have complete air superiority anytime we want it which would change the entire strategic equation as well as the eventual political outcome.

The SA400 is specifically designed to defend against high level bombing attacks and formations, not stealty low level fast movers which is why they have a separate batter to defend them which has proven to be rather easily defeated.

Defeat one and kill both.