PB value is based off the best player in the league.

Last year it was Bonds with a 1421 OPS & 10.3 PB
This year its Lee with a 1106 OPS & 10.7 PB

So a team with players that have 900 OPS last year had PB values dramatically less than Bonds. This year that same 900 OPS scores dramatically more PB value.

Then again I could be wrong. : )

If you want to use PB value, the important thing is to find the ave. in a league this year and compare to that. That is a number that will have some meaning, giving you an idea if you need to cut some players and/or if you have a chance next year.