Sale 1: ~11 Keys.

https://backpack.tf/profiles/76561198847672167#!/compare/1555718400/1555804800

https://backpack.tf/profiles/76561198042175019#!/compare/1555718400/1555804800

Sale 2: Bulk.

https://backpack.tf/profiles/76561198337734785#!/compare/1562716800/1562803200

https://backpack.tf/profiles/76561198089253101#!/compare/1562716800/1562803200

Sale 3: ~10 Keys Pure.

https://backpack.tf/profiles/76561198164200492#!/compare/1556582400/1556668800

https://backpack.tf/profiles/76561198164200492#!/compare/1556582400/1556668800

Sale 4: ~11 Keys Pure.

https://backpack.tf/profiles/76561198841279602#!/compare/1557014400/1557100800

https://backpack.tf/profiles/76561198129731125#!/compare/1557014400/1557100800

Sale 5: Untrace.

https://backpack.tf/profiles/76561198854466685#!/compare/1559952000/1560470400

https://backpack.tf/profiles/76561198140790416#!/compare/1560556800/1561680000

Sale 6: Untrace.

https://backpack.tf/profiles/76561198015834883#!/compare/1561334400/1561939200

https://backpack.tf/profiles/76561198218562209#!/compare/1561852800/1561939200

Sale 7: Untrace.

https://backpack.tf/profiles/76561198218562209#!/compare/1561939200/1562198400

https://backpack.tf/profiles/76561198337734785#!/compare/1562025600/1562198400

Sale 8: ~11 Keys Pure.

https://backpack.tf/profiles/76561198159121016#!/compare/1560297600/1560384000 - https://backpack.tf/item/7839919932

https://backpack.tf/profiles/76561198255935874#!/compare/1560211200/1560384000

Sale 9: Use There.

Sold For Terror-Watt Crack Pot.

https://backpack.tf/profiles/76561198255935874#!/compare/1560211200/1560384000

https://backpack.tf/profiles/76561198199313686#!/compare/1560297600/1560384000

Sale 10: ~12 Keys.

Sold For Miami Nights Big Elfin Deal (12)

https://backpack.tf/profiles/76561198199313686#!/compare/1560470400/1560729600

https://backpack.tf/profiles/76561198414403301#!/compare/1560729600/1560816000

Sale 11: ~11 Keys Pure.

https://backpack.tf/profiles/76561198337734785#!/compare/1561507200/1561593600

https://backpack.tf/profiles/76561198432872721#!/compare/1561248000/1561593600

Sale 12: ~10 Keys.

https://backpack.tf/profiles/76561198196763853#!/compare/1561852800/1561939200

https://backpack.tf/profiles/76561198841279602#!/compare/1561766400/1561852800

Sale 13: Bulk.

https://backpack.tf/profiles/76561198841314980#!/compare/1560902400/1560988800

https://backpack.tf/profiles/76561198834678807#!/compare/1560902400/1560988800

Sale 14: Bulk.

https://backpack.tf/profiles/76561198834678807#!/compare/1562112000/1562284800

https://backpack.tf/profiles/76561198880377562#!/compare/1562630400/1562112000

Sale 15: ~13 Keys.

Sold With 4 Keys For Disco Beat Down Conquistador (17)

https://backpack.tf/profiles/76561198043868580#!/compare/1560297600/1560384000

https://backpack.tf/profiles/76561198345788867#!/compare/1560297600/1560384000

Sale 16: ~12 Keys.

Sold For Orbiting Fire Head Hedge (10) + 3 Keys In Items.

B/O Was 12 keys - https://bot.tf/stats/listings/MGVD5ZQM

https://backpack.tf/profiles/76561198257963452#!/compare/1560729600/1560816000

https://backpack.tf/profiles/76561198446317427#!/compare/1559779200/1560816000

Sale 17: ~11 Keys Pure.

https://backpack.tf/profiles/76561198337734785#!/compare/1561593600/1561680000

https://backpack.tf/profiles/76561198862108437#!/compare/1561593600/1561680000

Sale 18: ~12 Keys Pure.

https://backpack.tf/profiles/76561198080179568#!/compare/1555977600/1556064000

https://backpack.tf/profiles/76561198141716087#!/compare/1555718400/1562457600

Sale 19: ~10 Keys Pure.

https://backpack.tf/profiles/76561198374322393#!/compare/1555804800/1555891200

https://backpack.tf/profiles/76561198267750483#!/compare/1555804800/1555891200

Sale 20: ~11 Keys Pure.

https://backpack.tf/profiles/76561198337734785#!/compare/1557100800/1557187200

https://backpack.tf/profiles/76561198177231509#!/compare/1557187200/1557273600

Sale 21: ~10 Keys Pure.

https://backpack.tf/profiles/76561198177231509#!/compare/1557273600/1557532800

https://backpack.tf/profiles/76561198080179568#!/compare/1557446400/1557532800

Sale 22: Bulk.

https://backpack.tf/profiles/76561198145805427#!/compare/1556755200/1556841600

https://backpack.tf/profiles/76561198306288794#!/compare/1556755200/1556841600

Marketplace.tf Sales:

https://marketplace.tf/items/tf2/30658;5;u98

Sale 23: ~14 Keys. (Ccalling high)

May 9

$25.00 / $1.8 = 13.89 keys.

Sale 24: ~13 Keys.

May 24

$23.00 / $1.81 = 12.71 keys

Sale 25: ~13 Keys.

May 26

$23.59 / $1.81 = 13.03 keys

Sale 26: ~13 Keys.

May 26

$23.00 / $1.81 = 12.71 keys

Sale 27: ~14 Keys.

May 28

$25.99 / $1.81 = 14.36 keys

Sale 28: ~14 Keys.

May 30

$25.73 / $1.82 = 14.14 keys

Sale 29: ~9 Keys.

Jun 1

$17.05 / $1.82 = 9.37 keys

Sale 30: ~9 Keys.

Jun 11

$17.00 / $1.81 = 9.39 keys

Sale 31: ~13 Keys.

Jun 17

$24.49 / $1.84 = 13.31 keys

Sale 32: ~13 Keys.

Jun 29

$23.69 / $1.84 = 12.88 keys

Sale 33: ~12 Keys.

Jun 5

$22.00 / $1.85 = 11.89 keys

Sale 34: ~9 Keys.

Jun 11

$17.10 / $1.85 = 9.24 keys

Sales: 9/9/9/10/10/10/10/11/11/11/11/11/11/12/12/12/13/13/13/13/13/13/14/14/14, hopefully i'm right.

Going with 11-13 keys.

Thanks to scourge for the premium!