Taking the last month since there is enough data.

gladiator.tf stats: https://gladiator.tf/sales?item=Mirthful%20Mistletoe%20Killing%20Tree&at=2021-06-05T13:38:47.589Z

Mannco.store:

https://backpack.tf/item/9868207588

https://backpack.tf/item/10046282977

https://backpack.tf/item/9543528794

https://mannco.store/item/29236

$15.99 / $1.74 = 9.19 keys

$16 / $1.74 = 9.20 keys

$16.91 / $1.79 = 9.45 keys

https://backpack.tf/item/10153217884

Sale 1) on gladiator.tf page.

https://backpack.tf/profiles/76561199107865875#!/compare/1621814400/1621900800

https://backpack.tf/profiles/76561198101961806#!/compare/1621814400/1621900800

https://backpack.tf/item/10147095153

Sale 2) scm sale

https://backpack.tf/profiles/76561198095293350#!/compare/1621123200/1621209600

https://backpack.tf/profiles/76561198846105801#!/compare/1620950400/1621123200

Sale 3) 7 key + 21 ref (~7.5)

https://backpack.tf/profiles/76561198849751643#!/compare/1621123200/1621209600

https://backpack.tf/profiles/76561198095293350#!/compare/1621123200/1621209600

https://gyazo.com/1bed0463ea4ee870562bb2304386d735

Sale 4) 7 key + 40 ref (~8)

https://backpack.tf/profiles/76561198082152116#!/compare/1621382400/1621468800

https://backpack.tf/profiles/76561198849751643#!/compare/1621382400/1621468800

https://gyazo.com/447fd182c5b9103308651d65e6dd85e7

https://backpack.tf/item/10136934150

Sale 5) scm sale

https://backpack.tf/profiles/76561198197292179#!/compare/1620259200/1620518400

https://backpack.tf/profiles/76561198123496597#!/compare/1620172800/1620432000

https://backpack.tf/item/10046282977

Sale 6) untrace

https://backpack.tf/profiles/76561198063772079#!/compare/1621036800/1621123200

https://backpack.tf/profiles/76561199012413110#!/compare/1621036800/1621209600

Sale 7) 7 key + 18 ref (~7.5)

https://backpack.tf/profiles/76561198063772079#!/compare/1621123200/1621209600

https://backpack.tf/profiles/76561199098694108#!/compare/1621123200/1621209600

https://backpack.tf/item/9967805351 - dumped bots / untrace

https://backpack.tf/item/9968173029

Sale 8) on gladiator.tf page.

https://backpack.tf/profiles/76561198053768041#!/compare/1616889600/1620345600

https://backpack.tf/profiles/76561199103818277#!/compare/1620259200/1620345600

Sale 9) bot transfer

Sale 10) untrace

https://backpack.tf/profiles/76561198355520251#!/compare/1622332800/1622419200

https://backpack.tf/profiles/76561198365507674#!/compare/1621900800/1622332800

Sale 11) untrace

https://backpack.tf/profiles/76561198993686702#!/compare/1622419200/1622505600

https://backpack.tf/profiles/76561198355520251#!/compare/1622332800/1622419200

Sale 12) untrace

https://backpack.tf/profiles/76561198993686702#!/compare/1622419200/1622505600

https://backpack.tf/profiles/76561198014878903#!/compare/1622073600/1622505600

https://backpack.tf/item/9868207588

Sale 13) dumped to quicksell.store

https://backpack.tf/profiles/76561199004492301#!/compare/1620345600/1620432000

https://backpack.tf/profiles/76561199111073161#!/compare/1620345600/1620432000

then bot transfers and a sale on gladiator.tf page.

https://backpack.tf/item/9721325550

Sale 14) gift

https://backpack.tf/profiles/76561198085880346#!/compare/1620432000/1620604800

https://backpack.tf/profiles/76561198197292179#!/compare/1620518400/1620691200

https://backpack.tf/item/9677056898 - mannco.store transfer

https://backpack.tf/item/9664532274

https://backpack.tf/item/9640633984

https://backpack.tf/item/9659227142

Sale 15-16-17) bulk, 7 key + 25 ref each (~7.5)

https://gyazo.com/c1b35d85183ab09a49762924c58131b8

https://backpack.tf/item/9615587678

Sale 18) 7 key + 20 ref (~7.5)

https://backpack.tf/profiles/76561198146260252#!/compare/1611100800/1620172800

https://gyazo.com/cfda1177e3ebc6a1df2bca87add75eb9

Sale 19) 7 key + 40 ref (~8)

https://backpack.tf/profiles/76561198066058908#!/compare/1620086400/1620172800

https://backpack.tf/profiles/76561198849751643#!/compare/1620172800/1620259200

https://gyazo.com/3a1d80d656c4cfc843b91082852bb833

Sale 19) on gladiator.tf page.

https://backpack.tf/profiles/76561199107865875#!/compare/1620259200/1620345600

https://backpack.tf/profiles/76561198066058908#!/compare/1620172800/1620345600

then loot.farm

Sale 20) on gladiator.tf page.

https://backpack.tf/profiles/76561199098694108#!/compare/1621123200/1621209600

https://backpack.tf/item/9557061095

Sale 21) untrace

https://backpack.tf/profiles/76561198178372977#!/compare/1619740800/1619827200

https://backpack.tf/profiles/76561199107865875#!/compare/1619740800/1619827200

https://backpack.tf/item/9556395997

Sale 22) bulk?

https://backpack.tf/profiles/76561198045611871#!/compare/1620086400/1620172800

https://backpack.tf/profiles/76561198342161127#!/compare/1620172800/1620259200

Sale 23) untrace

https://backpack.tf/profiles/76561198379718122#!/compare/1619568000/1621900800

https://backpack.tf/profiles/76561198045611871#!/compare/1621814400/1621900800

https://backpack.tf/item/9555522251

Sale 24) untrace

https://backpack.tf/profiles/76561199057512868#!/compare/1620259200/1620345600

https://backpack.tf/profiles/76561199099031605#!/compare/1620259200/1620345600

Sale 25) on gladiator.tf page.

https://backpack.tf/profiles/76561199107865875#!/compare/1620604800/1620432000

https://backpack.tf/profiles/76561199057512868#!/compare/1620604800/1620864000

Sale 26) on gladiator.tf page.

https://backpack.tf/profiles/76561198197292179#!/compare/1621209600/1621641600

https://backpack.tf/profiles/76561199107865875#!/compare/1621468800/1621555200

https://backpack.tf/item/9551404086

Sale 27) obviously 8 key but keys dont matches

https://backpack.tf/profiles/76561198977594900#!/compare/1620777600/1621382400

https://backpack.tf/profiles/76561198095022965#!/compare/1620518400/1620777600

https://backpack.tf/item/9542432455

Sale 28) untrace

https://backpack.tf/profiles/76561198197292179#!/compare/1619827200/1620086400

https://backpack.tf/profiles/76561198055591330#!/compare/1619654400/1620259200

Total sales:

15 @ ~7.5 key

6 @ ~8 key

classifieds: https://gladiator.tf/listings/60b9f80e21fae0469558dbd5 going with 7.5 - 8