And they called me crazy for stocking up on those "over-expensive" GM weather-strips back in the day….they weren't cheap when I bought 'em, relatively, but they fit and function like a dream.
NOBODY makes them aftermarket with the end plastic pieces or the squiggly wire reinforcement (where applicable). If they could, I'm sure the price would be adjusted up accordingly. Plus, the hardness of the aftermarket seals are much denser it seems and don't accommodate with enough crush in my opinion. Plus, it is my opinion (no proof) they simply try to get over by molding Cutlass ends on Monte Carlo door seals.
I've only had one experience with aftermarket seals years ago after repainting my 84
H/O. Tried soff seal door seals and they were nicely made, but a tad short. Even with adhesive and minor stretching, they still fit like crap. Then I had to slam the crap out of the door to get it to close. After about a week of that crap, went to GM seals and never looked back.