Might as well include the new sale.

Sold for a Harvest Moon Safe'n'Sound(57 Keys with Overpay)

http://backpack.tf/profiles/76561198089009690?time=1434351600 -> http://backpack.tf/profiles/76561198089009690?time=1434524400

Sold for an Orbiting Fire Thirst Blood(18 Keys with Overpay), a Steaming Bubble Pipe(12 Keys with Overpay), and 19 Keys(49 Keys total)

http://backpack.tf/profiles/76561198123717811?time=1432969200 -> http://backpack.tf/profiles/76561198123717811?time=1433574000

Sold for a Dead Presidents Brainiac Hairpiece(42 Keys with Overpay), a Strange Festive Pro KS Force-a-Nature(~6 Keys) and a Bill's Hat(~2 Keys)(~50 Keys total)

http://backpack.tf/profiles/76561198083073025?time=1433574000 -> http://backpack.tf/profiles/76561198083073025?time=1433660400

Strange Festive Pro KS Force-a-Nature mini suggestion

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

$16.79

$16.90

$11.50

$11.97

$11.71

$15.19

$16.79

$16.00

$14.95

$15.00

$15.00

$15.63

$17.69

$14.26

$17.42

$14.97

$13.63

$14.08

$19.18

$79.86(lmfao what, ignoring this sale)

$16.01

$22.00

$16.90

$16.00

$16.10

$15.99

$15.47

$16.00

$15.34

$15.61

$16.10

$16.16

$17.23

$8.05

$14.00

$11.30

$15.00

The average comes out at $15.33(Roughly 6 Keys)

Sales seem to fit, 49-57 Keys should be fine.

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