Tread depth across all of the tire matters. Measure depth in all grooves, if the center grooves are deeper than both outer grooves, some of the wear is due to low tire pressure. Low tire pressure will make a slight camber issue appear even worse.

To clarify, excessive toe will cause more wear in a shorter period of time than camber alone. It will also increase camber wear as well. When camber is slightly out, the contact pressure across the tire is higher on one side than the other causing long term wear. When toe is excessive, the tire is scrubbing across the road surface causing it to wear rapidly.

Excessive castor will cause camber wear as well _IF_ the car is predominantly driven in a city / burb environment with lots of sharp turns and sandy road surfaces as the tire is now being held at odd angles and is sliding around much more than being held straight rolling down the highway.