You talk about a deal, this is it! My wife's family discovered this one.  It is a buffet serving Japanese, Vietnamese, and Thai food.  You get 2 hours to eat and drink (including beer, juice, etc) all that you want.  You just keep ordering until your 2 hours are up.  Keep in mind that at the 30 minute left mark, they won't take any more orders but you can still finish eating.  So order big early.

The $138 HK dinner price roughly equates to $18 US and that price is good only if you start eating before 6pm.  It keeps going up if you want to eat later.  The highest price is still only $168 HK or roughly $22 US, which runs between 7 - 9:30pm. 

They also have a special dinner price for senior citizens and children and it is $98 HK or a little less than $13 US.  As well, they have a lunch buffet (Central location only!) and the prices for that are $110 HK or $14 US for an Adult and $78 HK or $10 US  for children and senior citizens.  The good thing here is that the menu is the exact same as the dinner menu.

The restaurant is called YumAsian and it has two locations. 

Note:  Reservations must be made

1)  Shop 1, G/F, Car Po Commercial Bldg., 18-20 Lyndhurst Terrace, Central
     Tel:  2126-7265

2)  10/F, CTMA Centre, 1 Sai Yeung Choi Street, Mong Kok
      Tel:  3743-1977

Every time we go to Hong Kong, we just have to eat in a Japanese buffet restaurant.  The experience is always a favorite of mine.  For this trip we had to find a new restaurant as our old favorite in Tai Koo had closed it's doors.  My wife's family located a hidden gem within the South China Hotel at North Point.  The cost is around US $20 per adult.  But that is a deal, a very good deal because buffets in Hong Kong are not like those in the US where you get cheap food that isn't fresh.  The food is very good and the buffet also includes Kirin beer.  Yes, I bet they hate to see Americans walk in.  I can't see how they make any money at all. :-)  

This one is highly recommended but I think you will need to go with someone who reads/speaks Chinese.  The menu is all Chinese.  They may have an English menu but we didn't ask. 

Wada Japanese Restaurant
2/F South China Hotel, 67 Java Rd., North Point

This is within walking distance from the North Point MTR stop.