Salary and Private Property

What's the difference between capping salaries and limiting the number of products a person can own (like Jay Leno's cars)? It's a trick question. There is no difference--both are private property. So, why should the powers-that-be have the right to cap anyone's salary in the private sector? Think about it. Congress does not put any ceiling on their salary. It raises automatically. All they have to do is not to vote for the raise. Also, President Clinton raised the POTUS salary during his term.