Very good reply Ves, you have given me a few things to think of which I hadn't considered:
It seems like in your case, there is "a number", around 8 at which you would start getting interested, but then another multiplier is applied to the number to get a real opinion rating.
For example default value interest for you might be 8, and then for a company like MQG where one could easily think of a few obvious fundamental caveats we subtract one P multiple for each caveat (or divide by the total number of caveats) to get your "real value" opinion of P/E around 3-4.
That is a pretty interesting concept on its own.