Earlier quoted context omitted.
Why would you limit to only billionaires, and why would you compare it to all spend? Try funding pensions and healthcare by taxing the wealth of the top 0.5% and it doesn't sound so impossible.
It still sounds impossible I'm afraid. A realistic wealth tax probably caps out and around 2%, remembering that the net worth of very rich people is generally not liquid and can be difficult to mark to market. Any higher rate risks forcing the rich to have an asset fire sale, which liquidates productive assets and isn't really good for anybody. At six to seven percent you would force them to be entirely liquid and wo…
But yes, global co-operation to enable a large enough tax on wealth is not going to happen any time soon. A more likely scenario is that as automation develops and as the share of income that capital gets grows, the working class will end up in a position bad enough that capitalism will collapse and be replaced with something else. Hopefully with something better, but could also be worse.