I do use a water taxi to get the group from Tortola directly to St. John for a land based stay, as there is no direct alternative.

I got numerous quotes such as this one from some water taxis:

The private water taxi from Red Hook to Hodges Creek is $125pp. Customs, Immigration & Docking fees are $35 per person

That's $1500 with out the immigration fees one way.

There is no water taxi from CA on STT. So the taxi to Red Hook is still required as well.