They replied to my message saying caps are high quality made in Taiwan and not to worry about what the underside looked like. :facepalm:
Bunch of jokesters.
If
in one week I don't hear anything good about them, I'll lock this thread and conclude in the OP that these guys (or guy) are sleazy and we should stay away until there is solid contradictory evidence (such as someone buying from them and having a good experience).
One suspicion is that they may have bought secondhand Razer and Cooler Master keycaps for ultra cheap, then painted them, and now hope to find suckers to sell to.
I just don't want to draw negative conclusions too quickly. There are tens of thousands of plastics factories in Taiwan. Someone may be serious about entering this business, and may actually have the time and interest to produce customized keycaps.