This year I have had the pleasure of going on multiple junk/boat trips in Hong Kong, the last of which I organized (first birthday party in 4 years!). Junk trips cost anywhere from $300- $700 + per person, here is a little guide to keep the budget low, and the guests happy:
Hire a Hong Kong (Local) company. I recommend Viking or Jubilee. Viking boat prices are lower the earlier you book the boat whereas Jubilee boats are quoted the same a week prior to the trip.
I paid $6100 from Sai Kung for a 35 person boat, it would have costed $5700 from Central.
2. Food. Order good food on the cheap. Expat friends like expat food. I recommend Home Flavour, a little french catering company in Sheng Wan. I fed a party of 35 for $2500 full of quiches, pasta salads, cheese, meats, etc. The expats seemed to like it. I liked it. I recommend everyone to BYOB since not everyone drinks or have their own alcoholic preference.
3. Water Sports. Water sports normally come with a banana boat and wake-boarding for an extra $2000+. I think water sports are fun, but not particularly worth the price to pay per person since not everyone gets to use them. (due to time constraints). Make sure you check the condition of the ropes since a friends banana boat rope snapped off and whipped a girls face (requiring stitches)
4. Where to go. Most expats like to leave from Central (connivence or they don’t like to go to the “Dark Side” a.k.a. Kowloon). But from Central you can only go to Lantau or Clear Water Bay. While those destinations are fine, the best places to go are in Sai Kung. In Sai Kung, the beaches are beautiful, and the water is clean. Step out of the Island bubble and experience Hong Kong!