Many examples come to mind:
Early open reel wire recorders gave way to the ferric oxide magnetic tape recorder after WWII, and then to the 8-track, compact cassette, and now DAT. When I sold Hi-Fi, an Akai RtR deck with Dolby and auto reverse was easily a $700 purchase.
The specs on modern units are far superior at a fraction of the cost.
My first fax machine was second hand, the size of a small foreign car, cost as much, and used thermal paper. At present, a plain paper fax, copier, scanner, bread maker, cat pan cleaner is only about $250 and the instant rebate means they give you money.
Think about watches. A really good swiss-made jeweled wristwatch was a hundred bucks or more in the 1970’s. At present, I have a Seiko that I paid about 40 bucks for in the early eighties. Other than batteries, it’s still performing fine.
The oil burner that ran at perhaps 65% efficiency has been replaced by a 90% gas furnace, for nearly the same adjusted cost.
If memory serves correctly, the cost of an IBM Executive typewriter in the 1970’s would cover a basic PC today.
No more-now I feel really old.