http://backpack.tf/classifieds/search/526/11/0

seller for 18, some for 19 with nice parts, 20 with headshots

http://www.tf2outpost.com/trade/10438286

unsold at 19 for 5 days

http://www.tf2outpost.com/trade/10549304

selling for 20 (very new, won't count as unsold)

http://www.tf2outpost.com/trade/10448682

has headshot, unsold at 22 for 4 days

http://www.tf2outpost.com/trade/4419214

selling for 20, no luck in the past 2 weeks (probs changed price)

http://www.tf2outpost.com/trade/10135820

unsold for 20 in 2 weeks

http://www.tf2outpost.com/trade/10161879

has 4, unsold at 20 for 2 weeks

http://www.tf2outpost.com/trade/10544063

18 keys, if buyer adds monkey(1.66) so 18.33

http://www.tf2outpost.com/trade/10271301

unsold at 20 for a week, has snipers and dominations and heavies

http://www.tf2outpost.com/trade/10331567

unsold for a week at 20

http://www.tf2outpost.com/trade/10543172

selling for 19, not lucky in 6 hours

http://www.tf2outpost.com/trade/10414799

selling for 18

http://www.tf2outpost.com/trade/10539935

selling for 19

http://www.tf2outpost.com/trade/10546812

has headshots, selling for 21

http://www.tf2outpost.com/trade/10448839

unsold at 19 for 4 days

http://www.tf2outpost.com/trade/10509057

unsold for a day at 20

buyers are all lowballers. 20 really is impossible these days, and I found 18 a bit too rare to consider in the range. If you find 2 outliers at 20, those are my counter outliers