I assume you are talking about the downtown "Charlotte Amalie " ferry. It's always around 11 or 12 $ pp with bags a short crowded trip. Now if in a hurry and want to take the van alone it cost us 85 one time. You can order a private taxi to be standing by but I believe the taxi association caused them to raise prices so it is a lot more for that service. Though seems a little chaotic unless you have a particular reason, I would go with the flow and take the "load em up" vans. They fill quickly and you are usually the first stop a few minutes later at the ferry building.