I'm not sure if my English is good enough to express this, but what I meant is that there're some centain choices for those 104 key sets in the market, because they would be sold well. And the blank ones usually wouldn't be sold many, so KBC doesn't bring the blank ones to the market. And even they're not making any blank black set! In short, there's no blank black sets available even in the Chinese market.
Since there're some people showing their interest on the blank black sets, I just contacted the head of KBC to see if we could possibly get some . So the respond I got from him is that even though the blank black set is not available in the market, he can take custom orders about it which requires 500 sets as minimum order. Meanwhile he also offers 100 sets as minimum order for the Ducky 104 blank black sets, but it's more expensive than KBC's (he said the Ducky sets includes a retail box).
I know it doesn't really make sense, even I didn't understand either at first. But it's not about why they couldn't just simply remove the step of engraving, it's because the blank black sets are not for sale unless it's a custom order. It's like personally I really like those non-printed Topre key caps, but what if the Topre company only has printed ones for sale. I might just think the non-printed ones are much easier to make than printed ones. But for Topre, revenue is what they care about. Only limited number of people interested in non-printed ones would not influence their decision.