They earn as much as $15,000 a month on oil tankers, according to officials at two shipping companies. They have the right to ask to leave a vessel and be replaced if they don’t want to sail into the danger zone. The crews however, are the ones taking the greatest personal risk and some are still refusing the extra rewards. In general, compensation for the voyages has jumped since attacks on shipping began to slow traffic through Hormuz early last week. Pay also rose in the early part of the Iran war, when vessels were being attacked regularly inside the Persian Gulf.