Well, in theory you can get in for close to nothing... You can buy a cheap F ticket HKG-TPE one way or something, go to the wing early, enjoy it for a few hours, and when boarding time comes, say you don't want to go on your trip anymore, exit the airport and ask for a refund on the ticket. Of course, the ticket would most likely take a few weeks or months to get refunded...

of course, this should work for any airline and their lounges.... although I don't think anyone has ever tried it.. and I am sure the airlines will catch on to you if you do it more than once or twice, and possibly blacklist you..