No different that the US and Britain cutting off arms sales regardless of the lost profits to Iran when the fundamentalist revolution happened - just do it and find a different customer for the vehicles. The government breaks it's our word all the time (e.g. Natives, veterans, farmers, fishermen, the unemployed, etc) to people who aren't generally assholes, and who really need the help, so there's no reason at all to worry about the national "honour" if we scuttled the deal to provide weaponry to a pack of savages like the Saudis.
Fuck, turn around and sell the LAV's to Iran instead for no other reason than to royally piss off both the Saudis
and the current POSPOTUS's regime in the US.