Original iPhone dropped to a starting price of $399:
https://www.apple.com/newsroom/2007/09/05Apple-Sets-iPhone-Price-at-399-for-this-Holiday-Season/
And, for years, we had in the US had subsidized phones where you were locked into 2 year contract but that made the upfront starting prices lower (e.g. $199 for iPhone 3G at
https://www.apple.com/newsroom/2008/06/09Apple-Introduces-the-New-iPhone-3G/ and for many phones that followed). I used to be on AT&T and they never reduced my monthly bill once I finished my 2 year contract.
In the past, I tended to buy a middle amount of flash storage on the highest end non-Plus sized phones (Plus and non-Plus started w/the iPhone 6 and 6 Plus), so I might pay $299 + tax out of pocket every 2 years, get the phone unlocked at end of contract and sell it for maybe $120-$180. Going back further, I still have my invoice for an iPhone 4 for $199 + tax.