This data is for full - price phones, and does not include prices for subsidized phones made cheaper by carrier contracts — a practice that has largely disappeared. (recode.net)
The data only measured full - price phones over time and did not include prices for subsidized phones made cheaper by carrier contracts. (recode.net)
The carriers didn't make a profit on the old, subsidized phone plans, so they've benefitted from shifting the expense onto customers directly. (fortune.com)