Last suggestion 4 months old, needs an update.

Trade #1:

Sold for a Max's Severed Hat and 10 keys pure (~3.945 buds, rounding to 4).

http://www.tf2outpost.com/item/440,3175324048,152,5

http://www.tf2outpost.com/trade/23608031 < offer is in it, he posted in the trade what it sold for.

Trade #2:

Sold for a Max's Severed Hat and 17 keys pure (~4.397 buds, rounding to 4.4).

http://www.tf2outpost.com/item/440,3018480261,152,5

http://www.tf2outpost.com/trade/22892826 < says on the trade, it's also visible in a trade with the Max.

Previous (accepted) suggestion had two trades as proof as well, don't say it's "not enough" (if you were going to say that).