Not only that, but the amount of any contract that you sign in deals like this is based on the value of the last contract that you were signed to. You can't just sign anyone to a $20 million dollar contract. There is a service time scale before you can make the big bucks.
The reason Van Horn can do this is because of the size of his previous contract (which was some stupid multi-year deal that paid him 14 mill in the last year of the deal).