The taxis are waiting outside the port. There is a dispatcher and he is rationing the people to different vans. We had to wait until the van was compleet, even in a middle row people had to sit on uncomfortable seats.
We paid 5,50 $ per person for the ticket but thats 3 years ago.
But if you are going a little bit further you can find some private taxidrivers and they bring also smaller groups or a couple to the Falls. But I donīt know their prices.
But we saw this just leaving the port in the Van. Oh, in the Van you pay for a roundticket and the driver tells you the time, when heīs picking you up. Thats not the best way to handle it.
We were standing in the sun, without protection and had to wait for about 20 minutes, until our Van came back.
Take a look at portreviews, maybe they have more and better advices.