You need trade history or comment proof that the item was traded for keys. In these trades, you cannot be sure that they sold for their B/O's. For example, in the 2nd sale, http://www.tf2outpost.com/item/440,4012319952,340,5 , a Scorching Defiant was involved. You need to analyse and compare backpack history, find proof of offers in comments or screenies of trade history to prove a sale.

EDIT: Use this for help: http://forums.backpack.tf/index.php?/topic/6033-new-unusual-price-suggestion-guide-the-cheat-sheet/

an outpost link won't tell us much. show us bp history and what not

At least the second trade didn't sell for 38 keys pure. It was offered in a bulk trade for a scorching spartan.