I have been to one, they are very discreet and very choosy. You get off the lift at the appointed floor and all you see is a door that looks like a fireproof door leading to a stairwell. The one I had had an eye slit which looked like a 1920s speakeasy door. You rang the doorbell and someone would look through the hole to see who you were and then would let you in. Or not.
There was no sign or anything to tell you what was on that floor. Also if they did recognize you or perhaps you didn't give the right password or perhaps you didn't say "I'm with Richard Lee" they would not open the door.
This particular joint was in Causeway Bay pretty hot mostly Hong Kong or some PRC product. As this was handled by someone else I didn't get a glimpse of the prices, and of course with the crowd I was with there were no takeouts
.
I would think all of the fellow correspondence of our tight little community should seek to have some kind of year end Christmas party where we all go as a group one of these places.
Keep on mongering