Ah, of course, it depends on what you buy. But in most cases, you can desolder a switch and order a replacement one. I've had to repair a €70 Cyborg v7 keyboar

Ah, of course, it depends on what you buy. But in most cases, you can desolder a switch and order a replacement one. I've had to repair a €70 Cyborg v7 keyboard. The PCB is printed on a flexible substrate, so I went with a conductive ink instead of my soldering iron. Now, a few years later, it seems to be defective again, but it's transient, so hard to diagnose. If the membrane gets torn, you have to replace it entirely, and they are not really standardized, so you'd have to get a specific one. Moreover, keycaps do not seem to be standardized either on most membrane keyboards, so you have the same issue. I guess that's an area where having low volumes is a good thing: you can't do anything too specific, it wouldn't be worth it. So the individual parts are themselves really standardized.