First unusual suggestion ^.^

I could only find 1 real proof for this. Thanks to Spangni[대리구매]B for the proof.

http://imgur.com/0QGJp5V,a5KxbkP#0

Yes, I know, this is in some foreign language. But!

http://translate.google.com.au/#auto/en/%EB%A7%A5%EC%8A%A4%EC%9D%98%20%EB%A8%B8%EB%A6%AC

So we can see those items were trading for a Max's Head.

Taking the lowest range of all those items (keys) = 2.6 + 2.6 + 1 + 0.18 = 6.4 keys.

Max's head = 2.2 buds, so 6.4 keys = 0.27 buds = 0.3 buds.

2.2 - 0.3 = ~1.9

http://www.tf2outpost.com/trade/12035588/ - Here we can see that this is the same Max's head as the previous owner's.

http://www.tf2outpost.com/trade/12149939 - New owner.

And since I got the screenshots from the new owner, I can prove the exchange was real.

http://imgur.com/rwHptHs - Here's the Max's from the previous owner, showing its not a level 1 or 7 Max.

Not sure about this one:

http://www.tf2outpost.com/trade/11765626 - Selling it for 1 bud + 10 keys. Not sure what he sold it for in the end

Conclusion

Well, I hope I gathered enough proof to prove the value of this hat. If I'm missing something, just tell me! ^.^