I've only ever bought 1 PHB for each edition, because that's what I need. I didn't buy the revised 2E or 3.5 for different reasons. The revised 2E book didn't make enough changes to bother with buying the new edition. I objected to the 3.5 book because a friend realized that you could create a 4 page document with all the changes, so I just used that instead instead of shelling out $30.