It's not point for point, it's by point of itemization. Each piece of gear has a stat budget, and each stat costs a different amount per point.
AP costs half as much as Str. 2 AP costs as much as 1 STR, but 1 STR gives 2.53 AP to a ret pally with Divine Strength and Kings. But from the look of the graph, he's not counting Kings, just DS, so only 2.3, or 15% more from strength than AP.
And if he's not counting Kings, Agility would be about that far below Crit Rating. Agility doesn't apply to Exorcism or Holy Wrath, which are a big chunk of damage in Naxx.