Tax those whose income exceeds the desired upper limit. In other words, in addition to having a minimum wage you have a maximum wage, where the maximum wage is

Tax those whose income exceeds the desired upper limit. In other words, in addition to having a minimum wage you have a maximum wage, where the maximum wage is a multiple of the minimum wage (x1000, for example). Any income earned between the minimum and maximum wage would go untaxed, but exceeding the maximum wage results in incurring tax. In order for this to work, we would need to include a way to tax assets as well, as otherwise people could just put their money into assets.