Probably by about $20 bucks. The 'P' version has an unlocked multiplier. It makes OC'ing a bit easier, but traditionally you can OC a 'locked' version to the same frequency using 'FSB' method (reference clock) which just takes a bit longer.
Are there any estimates on the costs of the Bulldozer series. They said the 8130P will cost 320 bucks, then they said the 8150P will cost 320 bucks and 8130P less.