I’m not convinced the shop is gouging you or your son. Much depends on how much of the overheating story they were given when the car was towed in.
With any overheating problem a compression test should be performed right off the bat in my opinion but a shop may not do this based on assumptions from what they were told of the problem.
Continuing to operate a vehicle with a known problem is a huge mistake about 99% of the time. Leaking water pump leads to overheating which leads to blown head gaskets which can lead to other more serious engine problems.
Chronic, severe overheating will often score cylinder walls, cook piston rings, wash out crankshaft bearings/cams/lifters due to coolant diluted oil, etc.
In a nutshell, you may spend 1500 bucks on head gaskets and be left with an engine that is knocking (crankshaft, etc.) or smoking like a brush fire (cylinder walls, rings).
I’d be very antsy about spending this much money on head gaskets. Odds are the engine has suffered other damage to some extent although that may not be known without further diagnosis and/or a partial teardown.