The profit margins on Apple’s iPhone are almost twice as high as the iPad, highlighting how important the smartphone is to Apple’s business. In a court filing in its ongoing lawsuit with Samsung, Apple reveals that its gross margins for the iPhone were between 49% and 58% between April 2010 and March 2012.  That is almost twice as much as the between 23% and 32% margin for the iPad over the same period. Apple’s gross margin across all product lines was an average of 42.8%, according to figures compiled by Reuters.