Could Someone Explain This?

Admittedly, I am inexperienced so my guess is that I am just missing something.

I have seen a situation that relates to several coins, but I will just pick one to make my example.

I spend a fair amount of time looking through the PCGS Price Guide. Now in other forums, it has already been established that the PCGS Price Guide may be a bit inflated or "optimistic" as it was put by other members. So, when I look through it I take it with a grain of salt and mentally subtract about 25%-30% to gain a ballpark assessment of a coin's value.

Today I was looking through it and noticed that they value an MS63 2007-P Jefferson nickel at $8. OK, discounting the PCGS price as I do...this would translate to between $5 and $6.

At this stage of the game, aren't MS63 grades quite common among 2007 coins?

I mean if someone bought a brand new roll of 2007-P nickels when they first hit the banks, wouldn't more than half of them be MS63's and many be even higher?

Is that roll that someone bought last year for $2, really worth $200? I am guessing not so can someone provide the piece of the puzzle that is obviously absent from my reasoning?

Is this a flaw in the PCGS Guide or in my assumption that most new coins would grade that high?

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On a different, but related note, there was on other thing that baffled me. On the very next line in the PCGS guide, they showed that the same nickel with "Full Steps" was worth only $5. Worth $3 more because it doesn't have full steps? I am so lost!