Your 87 Salon grilles should not be plated at all. They should just be molded from plain black plastic. Supply and demand sets that price in the real world.
The Supreme versions had chrome plating and were painted black where needed. Let me add that although the 442 was based on the Supreme, they installed the black unplated Salon grilles and amber parking lamps in the painted lower front bumper. You know. Exceptions.
Since they were the same essential grille except for the plating, they used the same molds, just different catalog numbers depending on the finish. They did that a lot for all the models. You'd see several iterations of "part numbers" cast on the back of a grille or other parts. Usually, there would be an engineering part number and also any supersession numbers. This did not always correlate to catalog part numbers. So sometimes if you go on ebay and search for a catalog part number, you may not find all the stuff out there. Boxes and labels washout or get torn and unreadable, and the seller uses the "part number(s)" molded on the part to advertise. Again, these may or may not match catalog numbers. Just need to know what you're looking for. MOST of the time, aftermarket parts don't replicate all those numbers on the backs.
The difference is in the plating, obviously. Sure, if you can live with the "wrong" grilles painted all black, that would give you the appearance of using the "correct" all black unplated plastic. Just be forwarned that you probably would need to touch them up periodically where road debris beats the paint off on the chrome bits showing. It really just depends on what level of correctness you want to spend or can afford. And as for car show points process, although a keen eye and knowledgeable judges can usually tell repainted vs. bare plastic, you should never be docked points for painting grilles black to match the color of how yours came from the factory. It technically is the same grille piece after all.
Most anything used on the G-bodies were usually colored differently depending on the model. Like the H/Os and Monte SS, etc., using black lower windshield moldings and wiper arms or even the
H/O front/rear window trim being half-black along with the 84-86 Calais/Salon/442 headlight trim. Which is the weirdest use of black on bright trim I've ever seen.
