A '68 033 radiator is on a entirely different planet than a 69 340/318 HD radiator. Around 30% less for the 340/318?? That's like saying a restored 69 340 Swinger is worth only 30% less than an original 68 Hemi Dart/Barracuda
How do you know that just because it didn't leak before, it's corroded and worn so that in 2 months down the road it will start to leak? And you have proof it was in a function running driving car that got up to operating temperature and didn't leak? It's used item that commonly wears and the buyer cannot fully inspect and confirm that amount of wear inside the item. Buyer is taking a big risk that the item will function fine and will keep functioning fine for some time.
Swinger340 offered a 69 340 3 core radiator that has a fresh recore. A buyer can see and confirm that it's fresh. And he offered it for $200.