While I understand what you're saying, I think you're forgetting the fact that vast majority of people who have such PC are not just using them for gaming. We're also graphic artists, programmers, & etc.
I have no argument with that. IT has more than paid my bills for 15 years. For what average joe is wanting for to play on his 800$ TV the PS4 or even ps3 are plenty. Plug and play 1080p entertainment with a large selection of toys at their fingertips. These people are not interested in PC gaming.
My kid is saving for a ps4 and wants a PC too. If I can build him a 500$ PC that gives him the ps4 experience then Im all in. Unfortunately it's not feasible.