It may act on the whole market, but it doesn't have the same impact on every OEM.

It's a bigger issue for Valve than the console competition, who have established supply chains potentially with fixed prices for certain terms or at least more significant volume discounts, and proprietary compatibility hurdles binding their customers, so they can sell hardware at a loss if they want to.

If Valve sells the computers at a loss they run the risk of people buying them for other uses, without generating corresponding Steam profits.