Sellers:

http://www.tf2outpost.com/trade/27463516 - 20 Keys (Spec KS) - 5 Days

http://www.tf2outpost.com/trade/27495884 - 20 Keys (Spec KS) - Young

http://www.tf2outpost.com/trade/27495187 - 20 Keys (Spec KS) - Young

http://www.tf2outpost.com/trade/27281272 - 20 Keys - 35 Days

http://www.tf2outpost.com/trade/27317321 - 20 Keys - 30 Days

http://www.tf2outpost.com/trade/27350437 - 20 Keys - 26 Days

http://www.tf2outpost.com/trade/27469793 - 20 Keys - 5 Days - Untradable

http://www.tf2outpost.com/trade/27469662 - 20 Keys - 5 Days

http://www.tf2outpost.com/trade/27497411 - 20 Keys - Young

http://www.tf2outpost.com/trade/27492785 - 20 Keys - Young

http://www.tf2outpost.com/trade/27488294 - 19 Keys - 1 Day

Classifieds:

http://imgur.com/a/uBSHK

x5 19 Keys (1 Gifted)

x9 20 Keys (5 Spec KS)

Conclusion:

Damn, an Australium being unsold for a month at bp.tf price ;-; Multiple unsolds at current price. There's only 1 seller at 19 Keys on outpost but 4 valid sellers on classifieds. As the proof for 19 Keys appears to be quite small in terms of outpost trades, taking a conservative drop down to 19-20 Keys.