When we did the body on my 69 B vert the trunk extension panel was in bad shape, needed a lot of work.
I located the panel in nice shape, the seller wanted something like 3 hundred plus shipping. I passed and the body guy told me I should have grabbed it. There is not a lot of these panels available.
So if that 66 has useable doors and some decent panels plus any parts, the car is worth the money for anyone with that same car. Still a lot of money but I suspect the seller knows what original body parts are worth