The PS4 Pro and XBox One X do **NOT** render in 4k That's just marketing garbage.
They render in 1080p and use blurry upscaling to turn it into "faker 4k". You can do this on a PC also, and get higher quality.
No setup is going to render 3d at "native 4k" at 30fps until you spend $2k+ on a machine with a GTX 1080Ti, or RTX 2070/2080, or some kind of dual GPU SLI setup.
My Machine has a gtx 1080Ti, and I get 60-100fps at 1440p gsync, but if I was running at 4k I doubt it would maintain above 30fps at all times.
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As for saving money on buying used console CDs... Once you start counting the cost of software, it really depends what you want to play specifically. The PC has some super high quality F2P games, like League of Legends and DOTA2. Plus, Steam has incredible sales on games that are just a little bit older. You just put them in your wishlist and wait for them to email you that the games are on sale at 50-75% off. This builds a really awesome game library that you can carry with you from PC to PC -- unlike console games. I find it hard to believe that used console disks can be as cheap as this, but I also don't really care for console games so I've never looked into it.
I admit that if you already have a living room HDTV, then a Console can save money ($150?) by reusing that as a display... And while you could hook a gaming PC up to a living room TV -- using mouse/keyboard in the living room is super awkward.. And while you can use controller on PCs, you still need the mouse/keyboard to operate the machine. Plus, games typically have controller-aim-assist on console, but only sometimes have it on pc-controllers. So for someone who is just 100% all in on being a living room couch gamer, a console might make practical sense even if it's not the best graphics for the money.
A PC also becomes even more economical over 5+ years (assuming you don't have parts failures), because desktop GPUs get faster and cheaper every ~6 months. So every 2-3 years you can drop a new $200-300 GPU into a PC to make the graphics 2-3 TIMES faster.. while that console still keeps rendering it's blurry pixels as you wait for a new console to come out which costs too much at launch, doesn't typically run all your old games (which maybe you sold back to the used store anyhow), plus you are back into a new $120 a year subscription.
