I am not an expert and have no personal experience, but I understood that Lilja, Bartlein, Kreiger were high-end barrels. Timney and Geiselle are high end triggers but there are others that are comparable for less (see drop-in trigger comparison reviews for details). Besides that, the rest of the parts are mostly mil-spec or bling. There are brand names that put packages together with premium parts. They might chamber their own barrels, produce furniture with their brand, and machine billet uppers and lowers. They'd charge a premium brand price for warranty support and resale value.
That's my understanding. If I've got anything wrong, I'll learn more from this thread.
That's my understanding. If I've got anything wrong, I'll learn more from this thread.