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[Frogboy]

and krim, with your logic, you would have to mine an infinite amount of times just to come up with the mathematical calculations and numbers you'd get running those calculations.

in a more realistic sense, because there is a randomness factor involved, they want to make sure it is not overly weighted to gaining a highly profitable item more frequently and less junk so to speak.

they just want to know that the items that you get are balanced and fair for the level of difficulty put in to getting them. they aren't looking for exact numbers, just rough estimates because they know there will be deviance between players and their "luck factor."