I was about to suggest this with 1 useable sale, but then I saw the other suggestion.

Sold for a Blizzardy Storm Texas Tin-Gallon(1 with Overpay) and 3 Buds(4 Total)(Credits to Drusi for the screenie)

http://i.imgur.com/Pkxl7fi.png

Sold for a Strange Festive Pro KS Scattergun(41 Keys), a Strange Festive Pro KS Holy Mackerel(6 Keys), a Strange Pro KS Pistol(5 Keys) and ~3.8 Keys in Sweets

~58.8 Keys total(52.9 Keys with Overpay, 4.2 Buds when converted)

http://backpack.tf/profiles/76561198047850997?time=1415520000 -> http://backpack.tf/profiles/76561198047850997?time=1416113333

Strange Festive Pro KS Scattergun mini suggestion

All recent sales on the SCM(Keys: $2.49): http://steamcommunity.com/market/listings/440/Strange%20Professional%20Killstreak%20Festive%20Scattergun

$109.97

$120.00

$120.70

$57.49

The average comes out at $102.04(Roughly 41 Keys)

To support this:

http://www.tf2outpost.com/trade/24144116 Seller at 42 Keys

http://www.tf2outpost.com/trade/24114179 Seller at 42 Keys

http://www.tf2outpost.com/trade/24159841 Seller at 42 Keys

Strange Festive Pro KS Holy Mackerel mini suggestion

All recent sales on the SCM(Keys: $2.49): http://steamcommunity.com/market/listings/440/Strange%20Professional%20Killstreak%20Festive%20Holy%20Mackerel

$14.45

$14.00

$14.00

$14.41

$14.95

$23.00

$13.00

$13.00

$14.18

$14.95

$14.95

$17.98

$10.35

$11.47

$14.34

$18.00

$12.65

$7.49

$13.28

$12.30

$15.93

$15.85

$16.00

$17.19

$15.85

$15.91

$17.25

$16.50

$15.42

$14.20

The aveage comes out at $14.76(Roughly 6 Keys)

To support this:

http://www.tf2outpost.com/trade/21968179 4 Months unsold at 7 Keys

http://www.tf2outpost.com/trade/24007767 Seller at 7 Keys

http://www.tf2outpost.com/trade/24144336 Seller at 7 Keys

http://www.tf2outpost.com/trade/24134165 Unbumped seller at ~6.4 Keys

Strange Pro KS Pistol mini suggestion

All recent sales on the SCM(Keys: $2.49): http://steamcommunity.com/market/listings/440/Strange%20Professional%20Killstreak%20Pistol

$12.16

$12.16

$12.16

$18.64

$12.61

$12.65

$16.99

$16.73

$16.73

$15.52

$14.97

$14.92

$13.89

$9.99

$11.50

$11.50

$13.88

$16.09

$13.99

$11.31

$12.01

$12.65

$21.51

$10.00

$11.01

$11.01

$11.00

$11.47

$11.01

$12.65

$10.93

$16.07

$13.80

$12.45

$11.51

$9.19

$9.83

$9.99

$14.16

$9.94

$14.89

$14.10

$11.18

$11.00

$10.98

$9.01

$11.36

$11.35

$11.38

$9.47

$9.47

$13.01

$11.39

$11.26

$11.26

The average comes out at $12.58(Roughly 5 Keys)

To support this:

http://www.tf2outpost.com/trade/23999095 Seller at 6 Keys

http://www.tf2outpost.com/trade/24149390 Seller at 6 Keys

http://www.tf2outpost.com/trade/24058832 Seller at 6 Keys

http://www.tf2outpost.com/trade/24130051 Seller at 6 Keys

http://www.tf2outpost.com/trade/24133463 Seller at 5.5 Keys

To polar's reply on the last suggestion, It doesn't seem like it really sold for that aces ballcap, since he had both at the same time once: http://backpack.tf/profiles/76561198118719797?time=1412060400

The other two sales are too complex to use(oh the irony).

Two sales(And one practically being at pure), 4-4.2 should be fine.

Additional Proof/Counter-Proof/Constructive Criticism/Feedback is always appreciated.