Some key points:
- Pathfinder and D&D rulebook sales are not that different, except that Pathfinder does it with a handful of titles, while D&D does it with many. About 60-65% of each lines sales are rulebooks.
- Individual adventures are weak sellers for both brands, while Pathfinder has pioneered the "adventure path" model, which accelerates sales and folds in supplemental materials. If you included supplements and adventures in the same category for D&D, there wouldn't be that much of a sales difference between the two brands.
- Efficiency seems to be what stands out for Paizo. Fewer, better accessory books accelerate sales. Adventures and supplements, normally slow sellers individually, sell well when combined in adventure paths. Flip mats and tile packs are strongly supported by Paizo, with strong resulting sales, while WOTC intentionally phases out their tile sets.