$76.71
Description
Using data from http://css.umich.edu/factsheets/carbon-footprint-factsheet, CO2 generated averages 0.39 lbs / mile per person.
4684 mile flight from Tokyo to Juneau, 9368 miles round trip, = 3,653.5 lbs CO2 per person.
At $0.021 per pound CO2, round trip cost = $76.71 to offset