Actually for his production, based on NFL salaries, he's not overpaid, at least not by much. PFF ranks him as above average. Jerry Hughes of the Bills also gets $9 mil a year, and he's got only 1.5 more sacks this year, and makes about 1 more tackle a game. Carlos Dunlap has 2.5 more sacks and he makes $13 mil a year.
Crawford also can, and has, played both DT and DE. Position flexibility adds to a player's value.
At this point, with the defense playing well, I'd not be too quick to jettison him, perhaps re-work his contract, that'd free up money without losing him...