Well, that's not quite how it works, I'm afraid, and I don't think it's fair at all. Flying your CPH-OSL in the afternoon, for instance, gives you absolutetly nothing, regardless of how expensive you fare is! Similarly, flying an E-fare OSL-LHR gets you a seat faaaaar in the back and absolutely nothing for free, even though you've paid more than USD300 (+tax) one way. You get the same (nothing) if you pay USD 65 (+tax). It's just plain sad.

There's a reason the term P-class was invented... (who did, by the way?)