The point that everyone who talks about how inequality is bad is missing is that without the billionaire in your example, there would be NO jobs. Pure labor doesn't produce - there needs to be a business idea, vision, strategy, organization, sales - all those things that the businessman in charge provides.
The reality of the situation is that workers can be replaced - that's why they get paid less. But the businessman creator can NOT be replaced - without him/her in charge, there would be nothing else.
Soviet Union and other socialist countries tried taking the businessman in charge away - and we know exactly what happened after that.
I know this system isn't "fair", but it's better than the alternatives.