So here's the thing. Right off the bat it's hard to take you seriously when you don't even seem to understand how the pre-order works for the Steam Machine -- and that's even with me agreeing with at least some of your overall sentiment. What compelling reason would they have to shut down the pre-order page earlier than advertised?
Honestly, none of us really know for sure 100% factually whether the Steam Machine will sell out or not, but it's hard to take your questioning of it seriously when your understanding is so limited, and that's the nice way of putting it.
Personally, I won't be surprised either way. I suspect it will sell out, but like you, me, and millions (billions?) of other people, I also know that the price is laughable when appraised only by specs and anticipated performance metrics, so it also would not surprise me if they struggle with sales.