Since you mentioned it, I just added the Apple / Blackmagic eGPU to my 2018 Macbook Air and holy smoke it is a major change for docked 4k workstation with a mac laptop. This eGPU is underrated bigtime.
Very often "cheaper alternatives" have stability issues like crashing. Or plug / unplug problems. Stability is more valuable than the quiet although silence matters when the entire rest of your workspace is silent.
The build quality for these enclosures is obviously cheap and low quality. You can tell by when you work with the ports on them.
Also, none of these builds have been supported by Apple. This product was cooperatively designed with Apple so the support is excellent. You have one Thunderbolt 3 cable for all of the things to the mac.
So the price is actually good for what it is.