All I know is that your initial calculation was wrong. Furthermore, I don't understand why LyranaRae is limiting the scenario to buying a PI with 590 Xanax while treating the remaining 10 Xanax as profit.
If you actually receive 810,000 per Xanax sold, then 600 Xanax would yield 486,000,000.
Since a PI costs only 475,000,000, your gain is 11,000,000.
(486 × 2.2 = 1069.2;
486 × 2.3 = 1117.8)
Your actual profit margin falls between 2.2% and 2.3%.