59 Sport Coupe…..Pontiac sold less than 400,000 cars in 1959. While this was a relatively nice increase, it pales when compared to about 1,500,000 for both Chevrolet and Ford. This generally reflects the upscale positioning and price of our cars. With regard to NOS parts, auto manufactures produce and make available replacement parts, only to the extent they think will be needed, for a certain number of years after a particular model year (usually about 10 years.) The bulk of them are used up within the first 5 or 6 years. Fifty some years later, it's rare to even find parts made by the original manufactures, no matter the brand. The aftermarket helped to keep these cars going, mechanically for many more years, but things like sheet metal and trim have long since dried up. I don't think there is much of a price difference for any NOS parts for any brand. Chevy, Ford, Dodge, or Pontiac, they're all expensive.
With regard to reproduction parts, the old adage "what was popular then is popular now" holds true. It costs a lot to reproduce an old part. The investment only makes sense if you can sell many. That's why there is a proliferation of Tri-five Chevrolet, Mustang, Chevelle, and Camaro parts out there. There's not a whole lot of people out there looking for a 1959 Pontiac fender ornament. Pontiac popularity has mostly been focused on the GTOs and Firebirds of the 60's and early 70's.
The one bright spot for you, with this jackass in the White House for four more years, you'll soon be able to buy the entire Country for 10 cents on a dollar……John