You are paying for support and to make it easy.
But scale, as they sell more one assumes the markup will decrease.
Pretending to be a system integrator by buying proprietary Windows hardware and slapping Linux on it is a mug's game.
They were going to start building their own laptops at one point. I'm not sure what happened with that. Of course, nobody except Apple really builds their own hardware these days either (hence the term ODM).
disclaimer: I've never touched a s76 machine.
I would never run an OS that was pre-installed as the install image can't be verified.
I used to not have the option of buying Linux hardware, and it was terrible. I don't understand why anybody does that to themselves these days, and I sincerely hope we never go back to having to buy Windows hardware, slapping Linux on top of it, and hoping that enough devs had the _exact_ same hardware to minimize the glitches.