If he can show you all these examples of players making that same range of money for similar numbers, THEN HE IS NOT OVERPAID.
If there is precedent in the market for that pay for that production, then it isn't a situation where the player is being overpaid. I don't get what is so hard to understand. The market sets its own prices.
Sometimes the market sets a bad price.
A bad price for a certain team? Sure.
And a bad price for a certain player? Sure.
But if we can find all these similar players making similar money, then that is just the market price.
It's the same with big men, any big man who isn't a star making 10 million or so gets called overpaid by everyone. Yet there are many of these players at this pay range now. So it's just the market.
Maybe you don't want to pay that, so you make your choice not to, like Ainge has and he tries to draft young bigs (like Fab) and get by with smaller bigs. That's your decision as a GM. But if you want that 7 footer with that level of production, you are paying that price. It's the established price on the market.
Batum makes the same money as Green, they signed their contracts in the same offseason and they have virtually the same production. This isn't a coincidence.