Sale 1:

Sold for 29 keys + ~1 key in metal/items

http://www.tf2outpost.com/trade/27565079 - No B/O, seller confirms sale

Seller: http://backpack.tf/profiles/76561197977203883#!/compare/1457856000/1458025200

Buyer: http://backpack.tf/profiles/76561198154116714#!/compare/1457856000/1458025200

X = 30

Sale 2:

Sold with parted Strange Spec. ks Degreaser for Green Energy Hot Rod

No outpost link

Seller: http://backpack.tf/profiles/76561198013121180#!/compare/1460332800/1460505600

Buyer: http://backpack.tf/profiles/76561198055415266#!/compare/1460419200/1460505600

X + 3 = 33.5

X = 31

Sale 3:

Sold for Logo Samur-eye + ~2 keys in items

http://www.tf2outpost.com/trade/27981927 - B/O of 30

Seller: http://backpack.tf/profiles/76561198154116714#!/compare/1459555200/1459641600

Buyer: http://backpack.tf/profiles/76561198013121180#!/compare/1459555200/1459641600

X = 23 + 2

X = 25

Sale 4:

Bulk for Flies Anger

Seller: http://backpack.tf/profiles/76561198055415266#!/compare/1460505600/1460764800

Buyer: http://backpack.tf/profiles/76561198095443211#!/compare/1460419200/1460764800

Sellers:

http://www.tf2outpost.com/trade/28079528 - B/O of 35, declined 22 keys + 3 in items (offered below)

Sales at:

25

30

31

Current seller declined 25 (22 in pure), and 25 already looks like a bit of an outlier compared to the two other sales

Going with 30-31