using sales from 1st November and on

Sale 1

https://backpack.tf/profiles/76561197961309499#!/compare/1545177600/1545264000

https://backpack.tf/profiles/76561198253778785#!/compare/1538697600/1545264000

Sold for a pro KS Aussie Axethinuisher (6) + Ballonibouncer (1) + 351 ref in items= 14.47 Keys, rounding to 14 Keys

Sale 2

https://backpack.tf/profiles/76561198289821670#!/compare/1541808000/1542153600

https://backpack.tf/profiles/76561198059674109#!/compare/1541894400/1542153600

Bulk for a Starstorm Insomnia Modest Pile of Hat

Sale 3

https://backpack.tf/profiles/76561198140380043#!/compare/1545264000/1545782400

https://backpack.tf/profiles/76561198454615761#!/compare/1545696000/1545782400

untraceable

Sale 4

https://backpack.tf/profiles/76561198454615761#!/compare/1546041600/1546128000

https://backpack.tf/profiles/76561198238182322#!/compare/1546041600/1546128000

Sold for 15 Keys + 10 ref, rounding to 15 Keys

Sale 5

https://backpack.tf/profiles/76561198054689174#!/compare/1541376000/1541548800

https://backpack.tf/profiles/76561198454615761#!/compare/1541289600/1541376000

untraceable

Sale 6

https://backpack.tf/profiles/76561198345244699#!/compare/1543536000/1544572800

https://backpack.tf/profiles/76561198049638059#!/compare/1543449600/1543622400

Sold with 12 Keys in adds for a TF Logo Caribu (22) = 10 Keys

Sale 7

https://backpack.tf/profiles/76561198079049349#!/compare/1543536000/1543622400

https://backpack.tf/profiles/76561198049638059#!/compare/1543449600/1543795200

untraceable, cap doesn't match

Sale 8

https://backpack.tf/profiles/76561198454615761#!/compare/1542326400/1542412800

https://backpack.tf/profiles/76561198354072840#!/compare/1542412800/1542499200

untraceable, billycock doesn't match

Sale 9

https://backpack.tf/profiles/76561198080179568#!/compare/1544140800/1544227200

https://backpack.tf/profiles/76561198442234425#!/compare/1542758400/1544572800

untraceable

Sale 10

https://backpack.tf/profiles/76561198006544512#!/compare/1541462400/1541548800

https://backpack.tf/profiles/76561198188926265#!/compare/1541462400/1541548800

Sold for 14 Keys + 14 ref, rounding to 14 Keys

Sale 11

https://backpack.tf/profiles/76561198188926265#!/compare/1541548800/1541635200

https://backpack.tf/profiles/76561198053747026#!/compare/1541462400/1541635200

Sold with 45 Pure for a D@D Hot Dogger, bulk

Sale 12

https://backpack.tf/profiles/76561198053747026#!/compare/1543276800/1543449600

https://backpack.tf/profiles/76561198238743862#!/compare/1543363200/1543449600

Sold for 14 Pure + 20 ref, rounding to 14 Keys

Sale 13

https://backpack.tf/profiles/76561198238743862#!/compare/1543536000/1543622400

https://backpack.tf/profiles/76561198829365322#!/compare/1543622400/1543708800

untraceable

Sale 14

https://backpack.tf/profiles/76561198829365322#!/compare/1543708800/1543795200

https://backpack.tf/profiles/76561198311498888#!/compare/1543622400/1543708800

sold to stntrading, untraceable

Sale 15

https://backpack.tf/profiles/76561198311498888#!/compare/1543881600/1543968000

https://backpack.tf/profiles/76561198098339087#!/compare/1543968000/1544400000

untraceable

Sale 16

https://backpack.tf/profiles/76561198082869799#!/compare/1544486400/1544572800

https://backpack.tf/profiles/76561198245554948#!/compare/1544486400/1545523200

Sold for a duped smoking bonnet and a Skill Gotten Gains Bosten Breakdance, could be used on the bonnet

Sale 17

https://backpack.tf/profiles/76561198055622215#!/compare/1545523200/1545696000

https://backpack.tf/profiles/76561198243238038#!/compare/1545609600/1545696000

Sold with a Open Mind Vampire thingy for a Beams Puffy, less than 50%

Sale 18

https://backpack.tf/profiles/76561198055622215#!/compare/1546041600/1546128000

https://backpack.tf/profiles/76561198056793885#!/compare/1546041600/1546128000

Bulk for a Ghastly Ghost Headsplitter

Sale 19

https://backpack.tf/profiles/76561198259070324#!/compare/1542585600/1542758400

https://backpack.tf/profiles/76561198454615761#!/compare/1542499200/1542585600

untraceable, Keys were used to buy the searing plasma Towering Pillar of Hats

Sale 20

https://backpack.tf/profiles/76561198273381153#!/compare/1545264000/1545350400

https://backpack.tf/profiles/76561198168993666#!/compare/1545264000/1545350400

SCM

Sale 21

https://backpack.tf/profiles/76561198252511772#!/compare/1541808000/1541894400

https://backpack.tf/profiles/76561198454615761#!/compare/1541808000/1541894400

untraceable

Sale 22

https://backpack.tf/profiles/76561198454615761#!/compare/1542240000/1542326400

https://backpack.tf/profiles/76561198166418638#!/compare/1542240000/1542326400

Sold for 15 Keys + 20 ref, rounding to 15 Keys

Sale 23

https://backpack.tf/profiles/76561198061440669#!/compare/1541980800/1542153600

https://backpack.tf/profiles/76561198082754391#!/compare/1541894400/1542067200

Sold for a Spec KS Aussie Frontier Justice (11), Bill's Hat (2), Killstreak Pistol (23.58 ref) and 11 ref= 14 Keys

Sale 24

https://backpack.tf/profiles/76561198454615761#!/compare/1543795200/1543881600

https://backpack.tf/profiles/76561198082754391#!/compare/1543622400/1543881600

untraceable, Keys were used to buy the Noble

Sale 25

https://backpack.tf/profiles/76561198454615761#!/compare/1544227200/1544313600

https://backpack.tf/profiles/76561198055347766#!/compare/1491350400/1545609600

untraceable

Sale 26

https://backpack.tf/profiles/76561198346569299#!/compare/1542067200/1542240000

https://backpack.tf/profiles/76561198454615761#!/compare/1542240000/1542326400

untraceable

Sale 27

https://backpack.tf/profiles/76561198303898122#!/compare/1542153600/1543104000

https://backpack.tf/profiles/76561198454615761#!/compare/1542240000/1542326400

Sold for 15 Keys and 28 ref, rounding to 16 Keys

Sale 28

https://backpack.tf/profiles/76561198104859700#!/compare/1545868800/1545955200

https://backpack.tf/profiles/76561198314160142#!/compare/1545868800/1545955200

untraceable

Sale 29

https://backpack.tf/profiles/76561198104859700#!/compare/1545868800/1545955200

https://backpack.tf/profiles/76561198350879574#!/compare/1545868800/1546041600

gambling

Sale 30

https://backpack.tf/profiles/76561198256641496#!/compare/1543536000/1543622400

https://backpack.tf/profiles/76561197993826799#!/compare/1543276800/1543622400

untraceable

Sale 31

https://backpack.tf/profiles/76561198182030757#!/compare/1543276800/1543363200

https://backpack.tf/profiles/76561198256641496#!/compare/1543190400/1543276800

Sold with 20 ref for 15 Keys, still rounds to 15

Sale 32

https://backpack.tf/profiles/76561198097271466#!/compare/1543190400/1543276800

https://backpack.tf/profiles/76561198182030757#!/compare/1543190400/1543276800

Sold for 14 Keys + 15 ref, rounding to 14 Keys

Sale 33

https://backpack.tf/profiles/76561198271935035#!/compare/1541203200/1542326400

https://backpack.tf/profiles/76561198097271466#!/compare/1541030400/1541203200

Sold for 13 Pure

Sale 34

https://backpack.tf/profiles/76561198268005140#!/compare/1545177600/1545350400

https://backpack.tf/profiles/76561198454615761#!/compare/1545264000/1545350400

Sold for 12 Pure and 3 ref, rounding to 12 Keys

Sale 35

https://backpack.tf/profiles/76561198123320032#!/compare/1544313600/1544400000

https://backpack.tf/profiles/76561198268005140#!/compare/1544313600/1544400000

untraceable

Sale 36

https://backpack.tf/profiles/76561198002757046#!/compare/1544140800/1544227200

https://backpack.tf/profiles/76561198123320032#!/compare/1544140800/1544227200

Sold for 13 Keys and 10 ref, rounding to 13 Keys

Sale 37

https://backpack.tf/profiles/76561198255674690#!/compare/1541980800/1543968000

https://backpack.tf/profiles/76561198002757046#!/compare/1543881600/1543968000

untraceable

Sale 38 - 52

https://marketplace.tf/partneritem?sku=30658;5;u96&attrib=bp

Sold on the 1st November for 29.99$ (1.72)

= 17.42 Keys, rounding to 17

Sold on the 7th November for 21.00$ (buyorder)

Sold on the 8th November for 29.99$ (1.77)

= 16.94 Keys, rounding to 17

Sold on the 10th November for 31.00$ (1.77)

= 17.51 Keys, rounding to 18

Sold on the 15th November for 28.00$ (1.73)

= 16.18 Keys, rounding to 16

Sold on the 16th November for 21.15$ (buyorder)

Sold on the 20th November for 26.00$ (1.72)

= 15.11 Keys, rounding to 15

Sold on the 28th November for 28.80$ (1.71)

= 16.84 Keys, rounding to 17

Sold 2 times on the 16th December for 27.79$ (1.65)

= 17.06 Keys, rounding to 17 and 17

Sold on the 18th December for 27.98$ (1.64)

= 17.06 Keys, rounding to 17

Sold on the 25th December for 29.90$ (1.80)

= 16.61 Keys, rounding to 17

Sold on the 27th December for 35.99$ (1.79)

= 20.10 Keys, rounding to 20

Sold on the 30th December for 34.84$ (1.79)

= 19.46 Keys, rounding to 19

Sales: 10 / 12 / 13 / 13 / 14 / 14 / 14 / 14 / 14 / 15 / 15 / 15 / 15 / 16 / 16 / 17 / 17 / 17 / 17 / 17 / 17 / 17 / 18 / 19 / 20

https://gyazo.com/d07a1975872090e41576d4be1fd882c1

Going with 13-17 as per Erik's advice