Yeah, besides, I don't really think the clear tops are the reason people go crazy over nixdorfs. Obviously it is part of the allure, but they are also incredibly smooth which, at least for me, is the most important part of a linear switch. It's the whole package, and I think that could be said about korean customs. Quality machining, quality anodizing, premium features. (Not to say that a KMAC doesn't have that, but as billnye said, the added feature in a lot of OTD keyboards is the brass insert)
If you are paying groupbuy price, an OTD keyboard won't be much more than a KMAC anyway.
Yes, 356 series boards can become incredibly marked up due to their rarity and desirability, but the same could be said for click clacks and not many people question click clack values (To an extent)
Just my quick thoughts