The computing power in an iPhone 6 would have cost $3.56m in 1991

"This weekend, I saw a tweet flash by with an amazing claim: "If you had bought the computing power found inside an iPhone 5S in 1991, it would have cost you $3.56 million."
This statistic was originally put out by Bret Swanson, writing in Tech Policy Daily in February. He used a back-of-the-envelope calculation based on 1991 prices for memory, computing power, and bandwidth.
It's not precise, but it's safe to say that a lot of us are carrying, in our pocket, a computer that would have been unspeakably costly in 1991."

Source:  Matt Rosoff, Business Insider, 23rd December 2014

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