After reading a few posts in this thread, I start to realize why GMK can still prosper despite being ABS plastic.
They're not only key caps for the users - they're source of fascination in color combinations, and thick ABS typing feel.
So the users can ignore the pseudo-non-hygienic looking ABS shine on the caps when it comes, and they're willing to live with it, with their beloved toy, a source of visual inspiration.
It's freaking insane: some ABS plastic caps are standard and come with no extra charge on keyboards, and some are like $200 per set, and have to be shipped from Germany to the US before being shipped to Germany again before I can have it.