The qualifying offer for Duren is ~\(10m. The first season of Detroit's latest offer would be ~\)40m. If he took that $30m difference and invested it, he would earn more over the next 5 years than he would by taking the QO this year and getting the max from another team next year.
He can defer his taxes. But even if he doesn’t and let’s say he only has a \(15 million difference to invest after paying his income taxes, that \)15 million compounded over 5 years with an average annual rate of return of approximately 8% would yield an additional $7m.
That’s only looking at the $30m difference for the first year alone, and that’s only looking at the compounding interest of the amount he’d be left with after taxes, and using a fairly conservative 8% rate of growth.
Looking at it a different way, if he took the full \(40 million from the first year of the deal that Detroit is offering him and invested the \)20 million he was left with after tax for 5 years with an 8% annual return, the \(20 million post-tax income from that first year alone would become \)29 million in five years.
Meanwhile, if he took the full 10 million from his qualifying offer and invested the \(5 million he was left with after tax for 5 years with the same 8% annual return, that \)5 million post-tax income would become $7 million.