From memory.....costs may be a little off, but close. All costs are per person, one way:
Ferry $60
Luggage $5/bag (including carry on roller bags)
BVI departure tax - $20
Gratuity for bag guys $as you please
Caribs in route - $5/ea
Taxi from CA ferry terminal to STT - $10 (incl tip)
All said and done, I usually figure ~$100 pp each way.
Bags are now $10 each and as you said, they make you check most bags as there isn't room to be dragging a roller bag into the seating area.
I don't think the $10 taxi to STT would include any bag fees or a tip. I think the taxi itself is a $10 fee.
