they probably will handle it like with the Steam Deck

- no loss

- but small profit margin anyway, to max reduce the price, to max increase adoption/reach

for Valve people using Steam on non Windows platforms is more important then making a big buck from Steam Machines (because this makes them less dependent on Windows, MS has tried(and failed) to move into the direction of killing 3rd party app stores before, and Windows has gotten ... crappy/bloated/ad-infested which is in the end a existential risk for Valve because if everyone moves away from PC gaming they will lose out hugely)