Are you trying to say that the iPhone 12 costs more than the iPhone 13?
The original question was about the 12 Pro Max 256gb. Here it is on the first link I found on Google for £999. The equivalent spec 13 is £1,149. Old phone models don't go up in price, they go down.
https://www.amazon.co.uk/New-Apple-i.../dp/B08L5RF15Y