Adderall is not a 75% D-Amp, 25% L-Amp mixture either by weight or molarity.
Both XR and IR Adderall as well as their generic counterparts are racemic mixtures of amphetamine. This means that the medicine contains equal proportions of the two AMP optical enantiomers, L-amphetamine and D-amphetamine. Enantiomers are any two molecules of a given molecular formula that are nonsuperimposable, mirror images of one another. Think of your own two hands!
The non-biological, or laboratory synthesis of amphetamine or any chemical that is optically active (i.e. D-amphet., L-amphet, S-ketamine, R-Ketamine), will generally yield the product in racemic mixture. In nature, however, only one enantiomer is produced. This explains the relative potency of Dexedrine in comparison to Adderall. The dextro-isomer of amphetamine shows a much greater affinity for receptors than does the levo-isomer.
In other words, the Adderall mixture is 50:50 by weight, but mg by mg, the potency of ADD is 20-30% that of DEX.
And if anyone is still wondering, M. Amphetamine is exactly the same as the non-generic. Any perceived difference in effect is totally psychosomatic.
IN SUMMATION, the cheap cereal tastes just as good as the pricey shit too. Don't be a snob and enjoy the pills while you have them