I don’t believe they actually make the hardware. I know sytem76 always just rebadges Clevo hardware. You were basically paying for Linux to be preinstalled and for the Linux focused support.
EDIT. Actually it looks like I was wrong about that. They do apparently at least make their own chassis’s unsure about the motherboard’s or screens though.
system76 does not make their laptops, they do make some of their desktop lines though. System76 however is large enough that they get input into what Clevo designs - they Clevo often changes the hardware internals, but system76 ensures that the new hardware still has linux drivers. (in some cases system76 has shipped a laptop with something announced as not supported on linux, but this is rare and the rest of the features still works, and this is only done for a feature they figure linux users wouldn't use anyway)
System76 has long been working on their own laptop - every few years they make a progress report announcement - but I don't expect to see it anytime soon.