Looking at this hat.

Sale #1

bp compare of buyer

bp compare of seller

untraceable

Looking at this hat.

Sale #2, 3, 4 and 5

Sold by/to Scrap.tf bots and is now on Marketplace.tf. Sales are untraceable.

Looking at this hat.

Sale #6

March 18 sale on Marketplace.tf. Sold for 25.99 USD = 15.38 keys.

Sale #7

bp compare of buyer

untraceable

Sale #8

bp compare of buyer

bp compare of seller

untraceable

Sale #9

bp compare of buyer

Sold to a bot

untraceable

Sale #10

bp compare of buyer

untraceable

Sale #11

bp compare of buyer

bp compare of seller

untraceable

Sale #12

Sold at auction for 11 keys 8.77 ref.

Sale #13

bp compare of buyer

Sold for Smoking Bat Hat. Even though the last suggestion is still in date, I believe it is no longer accurate. Without taking too much time, here is a good guess if its value:

Mini for Smoking Bat Hat

Sale #13.1

Sold at auction for 11 keys.

Sale #13.2

Sold on Marketplace.tf for 29.99 USD = 16.2 keys.

Sale #13.3

Sold on Marketplace.tf for 25.00 USD = 12.9 keys.

Also taking into account the last suggestion which was made off of this one, current bp sellers and Marketplace.tf seller, I am calling anything above 13 keys (from Marketplace sales) outliers.

In my personal opinion, the real value is closer to 14 keys, but for the sake of this suggestion, it makes no difference.

Taking 11-13 keys.

Sale #xx

I was not able to find which sale it was.

May 14 sale on Marketplace.tf. Sold for 25.99 USD = 13.68 keys.

For being much too close and for having no evidence against it, 14 key sale is not an outlier.

Calling sale #6 an outlier.

Finally, from sales #12 and #13, I find the low value, and from sale #xx, I find the high value.

Going with 11-14keys.