The belts and buckles were used for several years. When the belts are “restored” the webbing, tags and button emblems are typically replaced.
If these are real, period pieces, the seat belt emblem button is the most valuable part in my opinion. I would want those to be reused, since the reproductions are different.
My best guess is $50-75.00 per occupant or $200-300 for a-set of four 1968 belts.