In the essay 'Famine, Affluence and Morality', Peter Singer looks at the ethics of 'How much is enough'. When we know there are people struggling, what are the ethics around our own level of consumption? What are our obligations to others? How much is doing enough? Toby Ord is part of the Effective Altruism movement which looks critically at where, how, and why we give. He is the founder of 'Giving What We Can' and has committed to capping his own 'allowance' at £18,000 and giving away the balance of what he earns.
In discussing the project I am involved in working on to build a Community Wealth Fund that pays a Universal Basic Income to 150 people, I was pointed in the direction of leanFIRE. F-I = Financial Independence. R-E = Retire Early. If you combine the concepts of building an engine to finance your expenditure with lean living, the size of the engine required comes down. The leanFIRE group discuss a Sustainable Withdraw Rate (SWR). This is what the Engine would need to earn to pay the amount you need sustainably. 3% seems a sensible figure.
If you combined Toby Ord's approach with a SWR of 3%, you would need a £600,000 engine. To pay a Universal Basic Income roughly equal to the median income per person in the world (c. £180/month) you would need an engine of £72,000 (3% is £2,160). The median income per person in the UK is about £21,000. The UK is a rich country. Toby isn't being a martyr, but living on that amount in the UK still requires some tough decisions.