An iPhone would have cost $3.5 million to build back in 1991, according to back-of-the-envelope-math by TechPolicyDaily.

Here's how the site reached that astronomical sum:

GB flash memory : $45,000 in 1991 vs. $0.55 today.

: $45,000 in 1991 vs. $0.55 today. Thus, 32GB flash memory = $1.44 million.

Apple's processor , which produces about 20,500 millions of instructions per second: $620,000 in 1991.

, which produces about 20,500 millions of instructions per second: $620,000 in 1991. The cost of mobile communication in 1991: $100 per kilobit per second.

in 1991: $100 per kilobit per second. The iPhone delivers speeds in the 15Mbps range today: 15,000Kbps (15Mbps) x $100 = $1.5 million.

Add those rough numbers ($1.44 million + $620,000 + $1.5 million) and you get $3.56 million. TechPoliceDaily also points out that sum doesn't even account for the iPhone's camera, operating system, display, apps, or motion detectors.

Wow.

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