El Salvador was the site of Ronald Regan's financing of death squads in the 1980s. The cost of preventing these crimes and terrorism pales in comparison to the official terrorism that was perpetrated on that country.

I'm not sure if there's a direct tie to Iran-Contra, but in Nicaragua Regan directly contravened a congressional funding ban and used Iranian and CIA drug money to fund the death squads there. Similar funding sources were probably at play in El Salvador.