Parts vs Accesories

I went to buy crossrails for my tahoe. The parts dept man looks up the part and said they are $86 per rail. I told him that someone on the phone said they would be $75 for the pair. He pokes around on his computer some more and figures out what is going on. Apparently there are "replacement parts" and "accesories". Same item at 2 different prices.
I asked him to look up a few other items. In general, "parts" cost about double what "accesories" cost. Why the price difference? According to the parts man many "parts" are in stock or can be delivered same day(usually), "accesories" take 1 to 5 business days.
Just something to aware of when you get things at your Chevy dealer.

Parts are something you either must have replaced because your car won't work, or your insurance company is paying to repair the vehicle. So cost isn't an option.

Accessories are something you won't buy if the price is too high.