If CO2 is the concern then include the CO2 in the price via a CO2 tax (or a per person CO2 budget if you want something objectively worse but more intuitive, th

If CO2 is the concern then include the CO2 in the price via a CO2 tax (or a per person CO2 budget if you want something objectively worse but more intuitive, then people can save up their CO2 credits for a cruise if they really want a once in a lifetime thing).