I know my translation doesn't literally refer to the product, but given that you mentioned that the context was a sales chart, I am assuming the other items are products sold through other sales channels?

The common English term for a retailer that contracts directly with a manufacturer to sell specialty or luxury items under strict conditions (the 制度 here), including price floors and display requirements, is "authorized dealer," "authorized reseller," or "authorized retailer." This system is often used in the luxury handbag market and other premium markets where the manufacturer wants to be selective about the retailers it selects so as to maintain a luxury image and prevent price competition from chipping away at the premium value of the product. Same with Apple products. Compare to drugstore brands that you can find at any old mom and pop store -- these are sold on the general wholesale market to anyone who is willing to pay the per-item price, and there are no restrictions placed on pricing, display quality, etc. at the retail level.

https://ecommerce-platforms.com/glossary/authorized-retailer
https://escholarship.org/content/qt46x0n36c/qt46x0n36c_noSpl...
(See other links below.)

If you must refer to the product itself, I think it's too awkward to do it without a phrase, something like "specialty items sold through authorized retailers" or "luxury cosmetics" (with a note that this refers only to items sold directly to consumers through authorized resellers). It's the department store brand (MAC) vs Lever 2000 concept.

I did find reference to the "price-maintained channel" on p. 16 of this publication, but honestly I think it was just a bad translation of the concept and should be changed. It's so literal that it cleaves the concept away from established lingo in the wholesale/retail world, so that a reader wouldn't really understand what they were trying to say. It's clear that this is not the terminology that would typically be used for this concept, and that this is not a type of sales channel that is unique to Japan. So I agree with you -- don't use this term, and don't reinvent the wheel. https://www.eu-japan.eu/sites/default/files/publications/doc...