http://www.tf2outpost.com/trade/10526034 5th offer is 17 keys (near to be accepted)

http://www.tf2outpost.com/trade/10570672 17 Keys offer

http://www.tf2outpost.com/trade/10606850 Selling for 18 keys

http://www.tf2outpost.com/trade/10552069 Selling for 18 keys

http://www.tf2outpost.com/trade/10285458 Have 3 Add for Machina (16 keys + 3 refs; 1 offer for 17 keys )

http://www.tf2outpost.com/trade/10286683 Sold for 18 keys (Very Good Strange Parts)

http://www.tf2outpost.com/trade/10571591 Sold for 17 keys (Quickselling btw)

http://www.tf2outpost.com/trade/7772383 Have an offer of 88 Refs (17.6 Keys)

http://www.tf2outpost.com/trade/10454447 16 keys (1 bought)

http://www.tf2outpost.com/trade/10538880 16 keys + 3 refs (1 bought)

http://www.tf2outpost.com/trade/10647277 Bought for B.M.O.C. + S.Invis Watch + 2 keys 16 keys in items + 2 pure)

http://backpack.tf/classifieds/search/strange%20machina Unsold at 19 keys (2 days)

http://www.tf2outpost.com/trade/10641002 New 19 keys (HS Part,Domin. Part)

http://www.tf2outpost.com/trade/10606850 Selling for 18 keys (Unsold 2 days)

http://www.tf2outpost.com/trade/10495453 Unsold for 19 keys (6 days)

http://www.tf2outpost.com/trade/10546812 Unsold for 20 keys (HS Part-4 days)

http://www.tf2outpost.com/trade/10135820 Sold for a Black + White Bill's which are 9 keys each 9 + 9 = 18 keys

http://www.tf2outpost.com/trade/10185543 Unsold at current range (19 keys) for 2 weeks

http://www.tf2outpost.com/trade/10651969 Selling for 18 keys w/ strange parts headshot and snipers killed

Sellers on outpost are all either high ballers at 1 bud+ or selling for 17-18

Successful buyers at < 19 keys:

http://www.tf2outpost.com/trade/10443600 Buying for 18 keys and got two in the comments agreeing to 18 keys one with a strange part

http://www.tf2outpost.com/trade/10454447 Added for machina at 16 keys

http://www.tf2outpost.com/trade/10535739 Bought 1 for 16 keys

Proof courtesy of Trip and 404 Spy not found. General consensus on other suggestion was that 18 flat would be a better reduction.

http://backpack.tf/vote/id/518a5aeaba25362930000004