Cost of iPhone X in 1957
Having a billion transistors is not 10 times as useful as 100 million transistors. The diminishing return kicked in even before that. Unless a killer application needs a billion transistors, the value created over a previous iPhone is incremental.I think a better way to measure value is   invention's cost effectiveness = price / (time * improvement to well-being)

The denominator is how much the invention makes our life better as measured by (the amount of time * the extent it helps).By this measure, smartphones are not bad but probably lose out to the Internet, washing machines, and air conditioners/heaters in hot/cold climate. Google is a pretty big improvement over older search engines and is worth quite a lot although the price we pay as privacy is not obvious.