In January 2012, Apple reported its best quarterly earnings ever, with 53% of its revenue coming from the sale of 37 million iPhones, at an average selling price of nearly $660. The average selling price has remained fairly constant for most of the phone's lifespan, hovering between $622 and $660.[32] The production price of the iPhone 4S was estimated by IHS iSuppli, in October 2011, to be $188, $207 and $245, for the 16 GB, 32 GB and 64 GB models, respectively.[33] Labor costs are estimated at between $12.50 and $30 per unit, with workers on the iPhone assembly line making $1.78 an hour.[34]