There is a large chance B offers to sell the ticket for less than $100 -- that is, he decides not to fly, and either forfeits his ticket or accepts a voucher fo

There is a large chance B offers to sell the ticket for less than $100 -- that is, he decides not to fly, and either forfeits his ticket or accepts a voucher for less than what he paid. That's the whole reason they overbook in the first place.