I'm halfway to green belt :D

Sale 1:

It + a Circling Heart Buckaroos Hat + 7 keys + a S.F Holy Mackerel sold for a Haunted Ghosts Master's Yellow Belt

(66.5*0.9) - 23 - 7 - (2.75*0.9) = 27.375 rounding to 27 keys

No outpost trade

Seller Before: http://backpack.tf/profiles/76561198065908363?time=1426143600

Seller After: http://backpack.tf/profiles/76561198065908363?time=1426230000

Sale 2:

It + 13 keys sold for a Duped Roboactive Bonk Helm

(50*0.9) - 13 = 32 keys

No outpost trade

Seller Before: http://backpack.tf/profiles/76561198056465795?time=1425970800

Seller After: http://backpack.tf/profiles/76561198056465795?time=1426057200

Notes:

Mini for the Duped Roboactive Bonk Helm

It + 5 keys sold for a Steaming Killer Exclusive

54.5- 5 = 49.5 rounding to 50 keys

Buyer Before: http://backpack.tf/profiles/76561198003188332?time=1420963200

Buyer After: http://backpack.tf/profiles/76561198003188332?time=1421049600

Conclusion:

Sales at 27 and 32 keys, taking the final range as 27 - 32 keys.