Proof below. Unusual overpay is applied.

First unusual suggestion, please help me along.

1st sale:

http://www.tf2outpost.com/trade/13989839 sold for 15 keys, outlier?

2nd sale:

http://www.tf2outpost.com/trade/13911569 sold for stormy storm l'inspecteur=19 keys

3rd sale:

http://www.tf2outpost.com/trade/13896134 sold for around 18 keys according to backpack history

4th sale:

http://www.tf2outpost.com/trade/13604474 sold for around 17 keys (54.33 ref, key and 40 ref sweets)

5th sale:

http://www.tf2outpost.com/trade/13165369 sold for 17 keys

6th sale:

http://www.tf2outpost.com/trade/13866927 sold for bubbling cosa, blood banker and sweets=~19 keys

7th sale:

http://www.tf2outpost.com/trade/14138050 sold for 21 keys

8th sale:

http://www.tf2outpost.com/trade/13911024 sold for 22 keys (bud)

9th sale:

http://www.tf2outpost.com/trade/13844525 selling for 21 keys, sold for steaming sns and 6 keys=~21 keys

The only one selling on classifieds for 20 keys has already sold in the 2nd link.

Sales: 15, 17, 17, 18, 19, 19, 21, 21, 22

Most people start with a price of a bud, but usually accept lower offers. I see more solds below 20 keys, but there are still some that have sold for 20 to 22 keys.