This is cheaper in the same way I don't use a KVM and instead change the inputs in my monitor (Also, I'd have to figure out what DP KVM supports G-Sync and 1440p 165hz).
It’s impossible to find any KVM at any price point that works with 120Hz, and certainly not 120Hz@3840x1600. Forget about G-Sync.
I resorted to just keeping short USB and DP or TB->DP cable extenders plugged into the computer ports and have a “cable zone” where I just unplug and replug all the cables to switch machines. The short extensions are to protect the ports in the machines from wearing out.
It’s way cheaper than any KVM and it actually works.
I do dev and browsing work at 30hz and the only thing I notice is the little gaps when moving the mouse fast.
I just notice discomfort when my monitor isn't >90Hz or so. On Windows it occasionally will reset to 60Hz, maybe due to video card driver updates? I could probably re-adjust back to 60Hz in a few weeks but I don't see the point of going through the discomfort, especially when I occasionally do play games where the higher frame rate makes a much more drastic difference.
Level1Techs a small shop that I discovered via their YouTube channel. While they don't manufacturer the KVM themselves (all to common, see the OP link), they look to have done rigorous testing and compatibility analysis. They claim it works up to 3840x2160@120hz because it supports DP 1.4.
https://store.level1techs.com/products/14-display-port-kvm-s...
I actually did many days of research into assembling my own KVM. HDMI is surprisingly straightforward but DP is a nightmare of nested standards. Just one example: There is support for running i2c tunneled through another protocol. The biggest issue is the link speeds that a DP1.4 cable runs at. The chips needed to do the switching are expensive and pretty much need to be machine assembled. When you get to those frequencies the trace design and board composition even become a factor.
After all that I don't find the $299+ for a good KVM to actually be that excessive. It's surprising how difficult it is to electronically do "I unplug cable and plug another one in".
I don't even need stuff like display spoofing, etc, since I only use one machine at a time and don't constantly switch, but it was just way too much work to put together. If you only need slower link speeds it's doable.
