Wiktionary
apple tax
n. 1 (context slang English) the price premium paid by Macintosh users over that of a Wintel PC of comparable power and features 2 (context slang English) by extension, the price premium paid by consumers of Apple consumer products over comparable devices from competitors 3 (context slang English) the large cut of the gross paid to (w: iTunes) from every sale on iTunes by content providers, over how much a cut is given at other online retailers