It's not a big drop, but...

I'm lowering Cancer, i'm happy!

Sale 1

http://www.tf2outpost.com/trade/25175713 Sold for 69 keys pure http://i.imgur.com/LQWmnAO.png

B/O for TC was 6

X = 5.8

TC https://backpack.tf/item/473748219

Keys were probably used to buy this https://backpack.tf/item/2832031915i

Sale 2

http://www.tf2outpost.com/trade/23855829 Sold for 5 buds + 6 keys pure

B/O for TC was 5.5

X = 5.5

Pure https://backpack.tf/profiles/76561197971392967?time=1424678400#page0

TC https://backpack.tf/item/473748219

The keys' item ID shows it was involved with the Buds

Sale 3 That's an outlier.

http://www.tf2outpost.com/trade/24216796 Sold for 98 keys (6.5)

X = 6.5

Keys https://backpack.tf/profiles/76561198072487593?time=1421481600#page0

TC https://backpack.tf/item/1816695815

Sale 4

http://www.tf2outpost.com/trade/24396096 Sold for lev 38 Max + 35 keys pure

B/O for TC was 6

X = 3.3 + 2.3

X = 5.6

Max https://backpack.tf/item/274994612

Keys http://gyazo.com/b51c114832c1bf6c1bc52d72b34fb621

TC https://backpack.tf/item/1344642887