Thing is, with that $800 PC you can choose to play games at 1080p max settings. With PS4 Pro you're stuck with the equivalent of medium-high settings in most games, regardless of rather you have a 1080p or 4K tv, because only a few devs are choosing to make a 1080p with improved graphics mode for their games on PS4 Pro.
The thing isnt even released yet, a lot of games and all games from now on will offer improved graphics for every TV setting
My point is, out of the 10+ games announced to have PS4 Pro game modes so far, only 3 have been announced to have improved graphics at 1080p versus PS4, Paragon, Rise of the Tomb Raider, and For Honor. Yes there will be more games that have a 1080p imprved graphics mode in the future, but since Sony left the choice up to developers I feel most of them will take the lazy route and only offer two modes, 4K with PS4 equivalent graphics and 1080p with supersampling and PS4 equivalent graphics.
On the other hand, that $800 PC can play almost every current game at 1080p very high/ultra settings at 60 fps. Many PS4 Pro games don't have improved framerate either, they still run at 30 fps.
Yes, PS4 Pro value is good, but it's not right for everyone.