My own studies have taught me that differences in income/wealth, no matter how great, are not of themselves instances of injustice. I have also become convinced that mutual respect (of a basic kind: taking one another into account) must be the ethic of justice: as this author noted, a requirement of mutual respect follows from a belief in human moral equality. [Mutual respect as the ethic of justice also follows from the observation that human beings have no choice but to effect choices.] I have found that, unlike equality per se, mutual respect can be efficaciously applied to the economy — with astonishing results for society. If curious, all that is related in "Equality Is All We Need" (here in Medium).