Earlier quoted context omitted.
Whatever percentage it needs to be ratcheted up to in order to ensure that everyone is fed and has shelter. Seems like we can work backwards to determine that?
what if it's more than 100% of their income :) are YOU prepared to pay let's say an 80% income tax and a 25% sales tax for example ?
Food too expensive? Robotics farming. More energy needed? Scale up solar, wind, and utility scale battery storage installations. Moar cheap transportation? Scale up bicycle and electric self-driving car manufacturing.
It _can_ be done. We simply need the will to do so. Work backwards, first principles style. We have lots of atoms and electrons, lets organize them efficiently for everyone's benefit.