tl;dr - authors estimate that millionaires will account for >70% of the remaining carbon we can emit while still staying under 1.5 C. Among billionaires, yachts account for over 60% of their annual emissions.
[Billionaire yacht ownership] implies a contribution to climate change that is up to 6500 times greater for these individuals than the global average of 4.5 t CO2 per capita and year, or up to 300,000 times greater than the contribution of the poorest, at 0.1 t CO2 per person and year
1.5 isn't "locked in" in terms of absolute carbon emissions, but it will be by roughly 2030 if we stay on our current trajectory. It's all but inevitable unless there's a rapid shift in fossil fuel consumption patterns starting, like, yesterday.