An iPhone would have cost $3.5 million 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
Thus, 32GB flash memory = $1.44 million
Apple's processor, 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
The iPhone delivers speeds in the 15Mbps range today. 15,000Kbps (15Mbps) x $100 = $1.5 million
Add those rought numbers ($1.44 million + $620,000 + $1.5 million) and you get $3.56 million. TechPoliceDaily also points out that that sum doesn't even account for the iPhone's camera, operating system, display, apps or motion detectors.