The PCGS price guide has the '83P @ $1 for MS63, which is right in line with every other clad quarter. However, it lists MS64 @ $21, and MS65 @ $55 which is indeed several dollars higher than every other clad quarter ever minted. What this suggests to me is that the "experts" deem that the supply of MS64+ 1983P quarters is much lower than all the others, which is very likely true for whatever reason. So, if you find an MS64+ 1983P quarter in circulation (which is unlikely, but possible), its "book value" is significantly higher than any other clad quarter.
Now with that said, "book value" and the amount that you can actually sell the coin for can, and often is, two very different numbers. Supply and demand is what determines selling price. Even if the supply is low, if there is little to no demand, the price remains low. To get anywhere near "book value" for one of these quarters - should you find one - would be to find a collector that collects MS64+ clad quarters. I don't imagine there are many.