That's an interesting question. I would have assumed that the bartenders are hired to tend bar and are paid like bartenders elsewhere, and I also would have assumed that the club ticket agents and "gatekeepers" were actually just airline check-in or gate agents who get that assignment.

Now the weird part: At one (smaller) club I once visited, I got the impression that they might have done different jobs depending on the day.

Incidentally, at a recent visit to the CO Presidents Club in IAH, I was going to ask the gatekeeper if she was an airline check-in/gate agent (because she was quite nice to me), but when I walked past, she was on the phone, so I didn't get to.

FWIW, I generally tip at the CO clubs (heck, he booze is free), but had no cash on me last week and felt guilty about not tipping. But I used to be a waiter.