This should be a really easy feature to put into place:
Once an auction expires and it sends the item back in the mail, include in the mail the amount that you put the item up for.
Reasoning: If you action 20 items, typically what we do is search out a comparable price before putting it up for auction. This takes a lot of time and is tedious. If we had the original auction price on the items in the mail, we could easily put those items back up for auction without having to remember what the previous price was.