Dear Ed;
$400 seems 'normal' these days.
Redaiator cores come in several sizes you just need to look in the catalog. Around $250 +/-. The labor making the straps & geting the niples in the right place @ $80 an Hr. goes fast.
This is "key part" in your car, perhaps one out of an industrial usage (forklift, generator) will work.
Good luck, John M....