Apparently a private luxury tour of Halong bay for 3 days with 6 people only costs $250 per person! This 'junk' had 2 bedrooms, 2 jaccuzi tubs, a sun deck, formal dining room, and a staff of 5. Granted upon further inspection everything was just a bit off- the arms fell off the deck chairs, the jacuzzi tub erupted water like the Bellagio fountain, and the bed was as soft as a plank of wood.
All things considered I'm pretty sure this is the 5 star standard for a junk in Halong. The lovely staff more than made up for any little defects in the accommodations. Our guide spoke fluent English and was a great pal. The chef made elaborate 5 course meals that were some of the best we had the whole time there. When he saw our enthusiasm for his artful vegetable carvings of birds and flowers he sweetly created a massive fruit dragon display for our final meal!
I'd definitely recommend these tours! Be sure to bring warm layers though...