K.

http://www.tf2outpost.com/trade/24044534 ~ Offered on NaB Charmer's with B/O of 1 bud

Mini for Charmer's

http://www.tf2outpost.com/trade/24239255 ~ Completed trade with a B/O of 1.2 buds at that time

http://www.tf2outpost.com/trade/22884585 ~ Sold for KaW Lucha = 2.4 * 0.9 = 2.2 buds

Mini for Lucha

http://www.tf2outpost.com/trade/24128008 ~ B/O of 2 buds 6 keys = 2.4 buds at this point of time

http://www.tf2outpost.com/trade/24156941 ~ B/O 3 buds, has been offered a Pro KS Strange Black Box = 1.6 * 0.9 = 1.4 buds but sale did not happen

Mini for Black Box

http://www.tf2outpost.com/trade/24005787 ~ Offered on a RA Plumber's = 1.8 * 0.9 = 1.6 buds

http://www.tf2outpost.com/trade/24229941 ~ B/O 3 buds

I would say that 2.2 is the outlier.

Feel free to counter or support my proofs.