It would be cool when making a trade for deckbox to save the card values at that moment in time. It's cool that you can see the current value, but having the value of the cards at that time is sometimes helpful :)

No kidding, I traded a Consecrated Sphinx for a bunch of Hex Parasites back when Sphinxes were like $5 and Parasites were $3-4, and now it just looks embarrassing. :(

I think both the initial state and the value over time are interesting.