Exactly. Douglas is pretty well-versed at getting max value for a player (and then some) and refusing to settle. If his value was identified as an early 3rd in negotiations then that's likely indeed how the league viewed him and little more.
The Jets drafted him with hopes he'd be a versatile inside/outside piece. Turns out he really can't play outside. Maybe he'll become one and his value will increase. Maybe he could have proven to become one with Rodgers. But Douglas is clearly banking on him not becoming that and the value he got today being about the max he'll ever be worth.