The 960m does sit in 6th place on the Steam hardware survey, with the 750m at 8th. In all, it would seem laptop based GPU's make up roughly 16 to 17% of total Steam PC users.
The go buy a monitor statement was in regards to the millions of Steam users using Console level PC's. I assumed, without real data granted, that most of those folks are using dedicated displays, so that would have been factored into the $400. I assumed this because living room PC gaming is still in it's infancy, and not yet a large part of PC culture.
Hux1ey made a good point in that a good number of those lower tier machines would be laptops as well. Not to beat a dead horse, but if you're getting a laptop with a 960m in it, it's most likely not $400 (although you can get mobile i7 laptops with halfway decent intergrated graphics for that much, but that would be bellow the console performance level.)
No, you don't have to factor in display into the PC budget, but in the real world, it very much IS a part of that budget for a vast majority of non laptop using PC users. I'm quite sure that the living room solution will at some point become defacto, but we're not there, not even close.
Consoles sell in the many millions BECAUSE of the accessibility due to the fact that most everyone has a TV, but we all know this. The fact that PC gamers always point out that you CAN is different from the reality of if you will. I have a HTPC that I listen to podcast and watch streaming shit while I do shit like post here, and vice versa I listen to music and podcast on my PC (which has it's own sound system as well) while we game on the console.
For reference, Valve had shipped 1 million steam controllers in the beginning of this year, and I assume (don't know) that not all of them are using them in the living room (like me).
They jumped the gun on the living room PC with the Steam machine, it's why I don't think it's yet to be that common (in addiction to my anecdotal observations) but like some pointed out here, the Steam link has been a much bigger success for them. I don't have one and have not gamed on one, but I'd be wary of the added network latency created in the Stream with regards to me gaming with one.
For all the arguing, the truth is, if a budget PC were all the console killer it was made out to be, it would be killing the consoles. Ask Valve about that market though.
Also, in searching for data, it's crazy how many times this thread came up on page 2. Yes, I looked at page 2