70% of the Steam users have a PC that's weaker than the Steam Machine[0]. These things will sell out, that's not the issue. The issue is that Valve probably won't have enough power to secure hardware deals to fulfill all the orders, thus limiting the growth of their hardware side.

[0] https://www.techpowerup.com/342970/valve-claims-steam-machin...

If they have a PC weaker than the Steam Machine, they were obviously not willing to pay for a stronger PC even when components were cheaper before, so how is the situation better now?