While I totally agree if you want to truly
know the quality of the signal you need a very expensive box to actually measure the tiny deviations, if the question is "can this thing handle 80Gbit of data", can't you just get a couple of USB4 chips or whatever and have one send a pattern at that throughput and have the other try and receive and confirm that pattern? That would give you a basic "yes/no" kind of answer of "can it send XGbit?" I agree the processing capacity for such a thing at retail isn't likely to be $40, but probably a good bit less than >$15k. After all, you can get For example, I don't need to precisely measure exactly how messed up the signal is to know if the HDMI cable works or not at a given resolution. I'll see the TV have issues displaying a picture. Either the picture is there reliably or its not. I'm not trying to fine tune the cable, I'm just trying to see if it generally works or not.
As for testing power delivery, its not that electrically complicated to put a few amps through a wire for a few minutes. That said, the user must be aware if the cable isn't up to the standards that the chip states you could have some serious issues on your hands, but I guess better to find out on the tester at the workbench or desk than at your bedside.