The thing is with comparing consoles to PCs you can't really compare apples to apples... Yeah the xbox can do 4k, but pseudo 4k or even native 4k - It's not comparable - It will almost always perform better (IQ and smoothness) on a 4k capable pc, as a 4k game on console will have a lot of the eye candy turned off.
It's like booting a game up on pc, turning practically all the graphical settings to low or med - THEN turning it to 4k. To do THAT on a pc, no, you DON'T need to spend £700 on a gpu. I picked up a 1080ti for £530 new for my mate a few months ago, which will destroy ANY game at 4k with everything turned to low/medium, most even at high/ultra settings.
I never really get the "PCs are soooooooo expensive compared to consoles" argument. Really... They aren't.
First... You always have the option to buy a last gen OR used gpu for dirt cheap - As soon as a new series comes out (generally once a year or so) the last gen, becomes cheap.
AND when coming to upgrade the gpu, selling the old card often cuts a lot of the outlay off - No need to buy a new system.
eg - I sold my gtx970 for £150... Got a used gtx1080 from a friend for £330... Just £170 for quite literally a completely new gaming experience. That simply isn't possible with a console.
Believe me I wanted to love the XBox-x... But it's not even in the same ballpark IMO... Image quality OR value - And still EXPENSIVE for what you get (as outlined below). It's actually one of the reasons I stopped with consoles after my £300 xbox 360 broke (and microsoft wanted like £150 to fix their crappy solder (RROD).
Personally, IF you're buying ONE game every month, I don't see the money as much of an issue;
Why? Plenty of places will offer 12/24 months interest free credit.
In those 12/24 months you'd save a few hundred quid on games alone. I have so many games I've bought for like £5 I don't even have time to play them. Most are AAA titles. PC games are DIRt cheap! Esp 1+ year old ones.
(IF you can'e get credit or can't get the outlay, then I can understand the initial outlay for a gaming PC is high, and the below does not hold as much weight (Because it wouldn't be an option)).
Lets assume you intend to keep your pc/xbox, as is, no upgrades, for 2 years... And you get 2years credit.
New game every month (month or 2 post release);
£40 a month x 12 = £480
£15 a month x 12 = £180
Year 1...
£400 xbox + £480 games + £38 xbox live = £918
£900 pc + £180 games = £1080
Year 2...
(£918) + £480 + £38 = £1436
(£1080) + £180 = £1260
=So by end of year 1, you've paid an extra £160 for - A MUCH better IQ experience +You've got a computer worth £££, as well as a gaming rig.
=By end of year 2, you've paid almost £200 LESS for the pc.
Let's say you wanted your console or (now paid in full for) pc to last 3 years;
Year 3...
£1954
£1440
=£514 better off with the pc.
-There is an argument you could sell the console games, reducing that £200 'saving' but technically, it's capital - You also own MUCH more expensive parts to sell on (eg i7's from 2013 (!!) STILL sell on flea bay for around £150-£180)!
Sell a 2 year old gaming rig vs a 2 year old xbox with a few games - Which do you think will return the most £££?
-And, even if you sold every game you bought for half it's value (doubtful) it STILL works out cheaper with PC games.
So... for me personally, it comes down to not price, but something people rarely mention - How much EFFORT and TIME you can be bothered spending on PC gaming;
PC gaming can be a pain... You can't just chuck the disk in and it works.
Last few games I've played I've actually had to read a GUIDE to get them to run properly... Took me hours. Benchmarking/testing/adjusting settings etc.
So... Can you be bothered with the hassle of PC gaming, for image quality, is what I'd be asking myself.
This is why I was hoping the Xbox would actually do proper 4k, I would LOVE to just chuck a game in and relax with proper 4k gaming, but knew even before it's release £400 was too cheap for that to be a reality. I'd DEFFO pay £400 for a console and £55 for every game if it was.