It's called Swanson's law, but the more general phenomenon is called Wright's law: the more of something you build, the cheaper it gets.

Conversely if we stop building stuff (e.g. nuclear reactors) they get more expensive.
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RT @_HannahRitchie
Cost of solar PV modules, per Watt 📉

In 1975: $115
In 2021: $0.27

That's 425 times lower.

https://ourworldindata.org/grapher/solar-pv-prices?yScale=log
https://twitter.com/_HannahRitchie/status/1614277784725229573