That prices were falling prior to deregulation and did not fall even faster after deregulation proves that deregulation wasn’t a factor.

If you’re coasting to earth in a parachute and someone gives you a cup of coffee to drink which does nothing to change your rate of descent, would you then attribute your descent to the cup of coffee?

You even say it yourself: There’s lots of reasons… but deregulation wasn’t necessarily it especially not in the axiomatic way you say when you say that by “first principles”, regulations increase prices.

E.g., regulations and legislation around marijuana access have decreased prices, the ultimate “price” being a stint in jail for possession.