so we can have a future record of the price so when its time to sell something similar.
That isn't entirely logical. Things sell at the price people are willing to pay, that something sold today for £400 doesn't mean that someone exists who will pay £400 tomorrow.
That isn't entirely logical. Things sell at the price people are willing to pay, that something sold today for £400 doesn't mean that someone exists who will pay £400 tomorrow.