A OEM key costs about.

You can get a good deal if you look around.

From my memory, I think it is mostly caused by fabs trying to produce / setup 3D NAND workflows that is congesting the supply chain.
Increased demand for the product only compounds the issue.

The 1060 would be good for 1080p, but strongly limiting in 4K. Better to take a 1070 or 1080, that will get you much further. A 1080 Ti is even faster, but it's up to you if this makes up for the rahter big proce increase between those 2.

Faster RAM would also be nice, like DDR4-3200 for instance.

Add an SSD to your PC, you'll thank me later. Best would be an M.2 SSD with at least 480GB if you get a MoBo which supports them. They're much faster than HDD, but also more expensive, which limits their size. So a HDD in reserve for non-speed-critical Data like pictures and videos will speed up your PC

You could opt for an Ryzen RS5 1600 or even 1600X instead of the 7700K. They're not as fast as the 7700K, but more affordable, have 2 extra cores and 4 extra threads which may come in very handy in the future and absolutely up to the task at hand. Plus, the platform is more modern and cheaper if you opt for a B350 MoBo. You will need to overclock the 1600 non-X though as it's base clock is rather low.

Finally, some little tip: Don't neglect the cooling of your PC. A cooler PC allows for more overclocking or less noise and is beneficial for the lifetime of your components. You may want to add some fan or 2 to a tower to cool it better. Best would be 140mm PWM Fans as they can rotate at lower speeds than 120mm fans for the same workload.

A single 8GiB DiMM?

I know RAM prices are high right now, but that's insane. First, 8 GiB are barely enough for the latest blockbusters, so much that it's the minimum requirement of some already. A couple of Games, like GTA V, are really RAM hungry and will have both a bad performance and shitty frametimes with only 8 GiB. Second, bandwith is halved, making the afermentioned problem even worse

And even with 16GiB RAM, that will probably only last for 2-3 years before it starts limiting, so 8GiB are a very bad idea

I'm currently trying to finalize one of my builds for a new rig. I've got one for Intel and one for an AMD Ryzen build so far.

Current rig: https://uk.pcpartpicker.com/list/tTzshq

Intel build: https://uk.pcpartpicker.com/list/f8LGzM

AMD Ryzen build: https://uk.pcpartpicker.com/list/MjrZ3F

I'm still in the middle of deciding whether to go for 1080p 144hz, so I can max the majority of my games and still have good performance, or go 1440p and get decent performance while also sacrificing some settings.

There's always something that prevents prices from falling down... f*ck it!

Ryzen chips can be a bottleneck at 1080p, even with a 4.0GHz overclock. Therefore, if you're going for a 1080p@144Hz screen, then with for Intel.

Having said that, with that 1080Ti you've listed, you could go with a high refresh 1440p monitor without problems.

It would do but I recommend an RX 580 over the GTX 1060 for just the extra bit of power.

Yeah, the thought with Ryzen not being suited for 1080p did cross the mind, for that I'd consider 1440p.

Atm I'm leaning towards Intel and besides, I can always save and modify the Ryzen build for another time as I'm not hurting for funds to build another rig if need be. 

I could, but I don't want to run into that habit of having to turn down settings (not talking AA or GTA V grass type settings). I'm already turning down settings with my 980 and my current CPU can't cut it well with Planet Coaster (their game is more CPU intensive than GPU, despite them asking for a 980 on their reco spec list). 

Well, most of those monitors with high refresh rates are either FreeSync or G-Sync. With a G-Sync one you could still take advantage of the high refresh rate while not having to lower your settings.

I typed out a reply a moment ago, but it seems VGC loves dying here and there and it deleted my reponse.

As much as I'd love to lean more towards 1440p 144hz, I don't really want to dial down settings as often. I had to do this with my 2012 build a lot more despite mates "promising" me that things would be fine, I'd rather not experience that with a 1440p G-sync monitor. I have the money, I just don't want to blow it on something that would end up being rendered useless. 

It might not have carried over as much to the retailer side of things (so yeah, tough luck for us consumers), but it was definitely the case. The market was oversupplied which caused prices to plunge. Remember, demand is only one part of the equation. The other is supply.