PortageKeeper wrote on Feb 11^th, 2013 at 1:50am:

So about $860/person if two are going in, while two are coming out. What about the first two going in, or the last two coming out? It would seem that someone would have to bite the bullet on these costs, on each end. Harlan, please let us know if you find it feasible to send a couple older canoes up there as rentals. Thanks.

May I suggest dividing by shares?
# paddlers / total cost

This way the first or last isn't hit any harder than the others. Some may want to stay in longer too.

I've got no skin in this. It's just worked for me in similar situations.