User blog comment:Care Level/Magic Sword Ahri: A Guide to Nashor's and Lich Bane./@comment-4888212-20150103174624

thats nice honey (grandmas version of cool story bro), but i must inform you that, while your math holds true for this exact time in the game, rabadons and deathcap will soon after skyrocket in damage far beyond anything you can do with your build. the double amplification and the 30% from deathcap multiply with each and every AP you get after this point, making you a big nice fluffy snowball, about to roll over the enemy team. while you actually deal the same damage at  8620g, you will deal substantially less damage at, say 10k gold or 12k gold respectively.

TLDR: worse assassin, worse mage.