What would happen to our society if a maximum income was implemented?

This is sort of the case when income tax is high. Businesses pay lower wages but then supplement income with a cheaper alternative (like a company car). I suspect you'd see more and more of the highest earning people having greater supplementary benefits, like a house, yacht, garage full of cars, holidays, etc.

All that said, we will always have high earners because the high earners control how the world is.