In some instances like Grant Hill, Camby, and McDyess I think being injury prone actually extended their careers because their knees weren't degenerated from all the minutes. So its possible Chandler could be a good player for a long time under the same idea if he's gotten past the unlucky injury bug.
Per 36, Chandler has averaged 10.5 points, 11.4 rebounds and 1.8 blocks for his career. And he's a really tough defender.
I really like him, and think he's just been hit with some tough breaks so far in his career. However, I think you're right there's just no way to justify a big money contract to a guy with that kind of injury history and production. Frankly, I think he's high if he thinks he's getting anywhere near the 12.75M his contract is on the books for next year.