Was looking for evidence on the C9 one, found this instead.

SALES;

http://www.tf2outpost.com/trade/22337658 Sold for Duped Arcana Marauder (mini at 4.6)

4.6 * 0.9 = 4.14 (rounding to 4.1)

Histories:

http://www.tf2outpost.com/item/440,2924488182,30425,5

http://www.tf2outpost.com/item/440,2964639820,400,5

http://www.tf2outpost.com/trade/22640288 Sold for OC Pyromancer (Outdated at 3.6, mini at 3.7) + Logo Toque (Outdated at 1.8, mini at 1.55)

5.25 * 0.9 = 4.724 (rounding to 4.7)

Histories:

http://www.tf2outpost.com/item/440,2924488182,30425,5

http://www.tf2outpost.com/item/440,2972130654,316,5

http://www.tf2outpost.com/item/440,2972130645,97,5

Toque mini:

http://www.tf2outpost.com/trade/21495755 Sold for 26 keys pure

No overpay on pure, = 1.5

http://www.tf2outpost.com/trade/21703427 Sold for Ghosts Mongol (~1.1) + Steaming Dixie (~0.7)

1.8 * 0.9 = 1.62 (rounding to 1.6)

Using 1.5-1.6.

Pyro mini:

http://www.tf2outpost.com/trade/22771286 Sold for Scorching Bombing (3) + sweets (~0.3)

3.3 * 0.9 = 2.97 (rounding to 3)

Histories;

http://www.tf2outpost.com/item/440,2972130654,316,5

http://www.tf2outpost.com/item/440,3005023315,249,5

http://www.tf2outpost.com/trade/22765601 Sold for Miami Belt (4.9)

4.9 * 0.9 = 4.41 (rounding to 4.4)

Histories:

http://www.tf2outpost.com/item/440,2972130654,316,5

http://www.tf2outpost.com/item/440,2994273667,110,5

Using 3-4.4.

Duped Marauder mini:

http://www.tf2outpost.com/trade/23142197 Sold for GE Dapper (~5.1)

5.1 * 0.9 = 4.59 (rounding to 4.6)

Histories:

http://www.tf2outpost.com/item/440,3064889978,400,5

http://www.tf2outpost.com/item/440,3064889971,252,5

Very little else going on with the duped one... using 4.6.

Let it ride.