On the internet, people often claim that. For example, hunters buy hunting trophies for x2 price compared to other traders, and thieves pay more for jewelry. However, I was unable to confirm this: any items that I've tested turn out to have the same price when trading with Kliff, Sebastian, Marlo, Seruk, and Urkrass.
I am, however, using Content Mod, Quest Pack, and Alternative Balancing of the Community Patch. Did they change item pricing? Or are special prices for certain items originally nothing but an illusion?