Using last month.

Sale 1:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1525392000/1525478400

Buyer: https://backpack.tf/profiles/76561198309978633#!/compare/1525478400/1525564800

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 7

Sale 2:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1525737600/1525824000

Buyer: https://backpack.tf/profiles/76561198152453477#!/compare/1503100800/1525824000

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 7

Sale 3:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1526428800/1526515200

Buyer: https://backpack.tf/profiles/76561198803190521#!/compare/1526428800/1526515200

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 7

Sale 4:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1527292800/1527379200

Buyer: https://backpack.tf/profiles/76561198387777886#!/compare/1526169600/1527465600

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 7

Sale 5:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1526860800/1526947200

https://backpack.tf/item/4557783978 - Buyer is untraceable

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 7

Sale 6:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1526774400/1526860800

Buyer: https://backpack.tf/profiles/76561198097728123#!/compare/1526774400/1526860800

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 7

Sale 7:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198358932637#!/compare/1525824000/1525910400

Buyer: https://backpack.tf/profiles/76561198198896481#!/compare/1525824000/1525910400

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 7

Sale 8:

Sold for 6 keys?

Seller: https://backpack.tf/profiles/76561198002757046#!/compare/1526256000/1526342400

Buyer: https://backpack.tf/profiles/76561198091002525#!/compare/1526256000/1526342400

X = 6

Sale 9:

Sold to a bot for 6 keys + 1 ref

https://backpack.tf/item/6025875936 - Seller can’t be identified

Buyer: https://backpack.tf/profiles/76561198305676157#!/compare/1525392000/1525478400

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 6

Sale 10:

Sold to a bot for 6 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198166427437#!/compare/1525564800/1525651200

Buyer: https://backpack.tf/profiles/76561198305676157#!/compare/1525564800/1525651200

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 6

Sale 11:

Sold for 6 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198002757046#!/compare/1525392000/1525478400

Buyer: https://backpack.tf/profiles/76561198100477765#!/compare/1525392000/1525478400

X = 6

Sale 12:

Sold to a bot for 6 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198199830342#!/compare/1526688000/1527120000

Buyer: https://backpack.tf/profiles/76561198305676157#!/compare/1526601600/1526688000

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 6

Sale 13:

Sold to a bot for 6 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198067128609#!/compare/1525824000/1525910400

Buyer: https://backpack.tf/profiles/76561198305676157#!/compare/1525737600/1525824000

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 6

Sale 14:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198095022965#!/compare/1526083200/1526169600

Buyer: https://backpack.tf/profiles/76561198118644686#!/compare/1526169600/1526256000

X = 6

Sale 15:

Sold to a bot for 5 keys + 15 ref

Seller: https://backpack.tf/profiles/76561198198896481#!/compare/1525824000/1525910400

Buyer: https://backpack.tf/profiles/76561198344933095#!/compare/1525651200/1525910400

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 5.5

Sale 16:

Sold to a bot for 5 keys + 3 ref

Seller: https://backpack.tf/profiles/76561198124076833#!/compare/1527811200/1527897600

Buyer: https://backpack.tf/profiles/76561198305676157#!/compare/1527811200/1527897600

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 5

Sale 17:

Sold to a bot for 5 keys + 3 ref

Seller: https://backpack.tf/profiles/76561198100477765#!/compare/1526601600/1526947200

Buyer: https://backpack.tf/profiles/76561198305676157#!/compare/1526860800/1526947200

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 5

Sale 18:

Sold to a bot for 2 keys + ~3 keys in items

Seller: https://backpack.tf/profiles/76561198803190521#!/compare/1526860800/1526947200

Buyer: https://backpack.tf/profiles/76561198386441509#!/compare/1526774400/1526860800

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 5

Sale 19:

Sold to a bot for 5 keys + 3 ref

Seller: https://backpack.tf/profiles/76561198832739804#!/compare/1527120000/1527206400

Buyer: https://backpack.tf/profiles/76561198305676157#!/compare/1527033600/1527120000

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 5

Sale 20:

Sold to a bot for 5 keys

Seller: https://backpack.tf/profiles/76561198060033840#!/compare/1525651200/1525737600

Buyer: https://backpack.tf/profiles/76561198358932637#!/compare/1525651200/1525737600

Bot.tf confirms: https://i.imgur.com/q98wGyl.png

X = 5

Sale 21:

Sold for Cyclone RPS

Seller: https://backpack.tf/profiles/76561198178035545#!/compare/1526515200/1526601600

Buyer: https://backpack.tf/profiles/76561198220299547#!/compare/1526515200/1526601600

RPS needs another drop, can be used on that instead.

Sale 22:

Scammed

Seller: https://backpack.tf/profiles/76561198220299547#!/compare/1526688000/1527120000

Buyer: https://backpack.tf/profiles/76561198832739804#!/compare/1527033600/1527120000

Sale 23:

Bulk for keys?

Seller: https://backpack.tf/profiles/76561198140162979#!/compare/1525737600/1525824000

Buyer: https://backpack.tf/profiles/76561198095022965#!/compare/1525737600/1525824000

Sales 24 & 25:

Sold for $25.54 and $21 on marketplace.tf

https://marketplace.tf/items/1113;5;u3004

Too high compared to current sellers/sales.

Sale 6:

Sold for Green Confetti Fruit Shoot + Lime paint (~2)

No outpost

Seller: https://backpack.tf/profiles/76561198152453477#!/compare/1525824000/1525910400

Buyer: https://backpack.tf/profiles/76561198286104741#!/compare/1525824000/1525910400

Way too high, excluding.

Sellers:

7 keys:

https://i.imgur.com/uzsbXIT.png

https://backpack.tf/item/6350522925

https://backpack.tf/item/5776390259

9 keys:

https://i.imgur.com/SNJaYwQ.png

https://backpack.tf/item/4446307800

10 keys:

https://i.imgur.com/xwGZ2Hp.png

https://backpack.tf/item/4213134363

40 keys:

https://i.imgur.com/XV7JRmH.png

https://backpack.tf/item/3032193653

50 keys:

https://i.imgur.com/AwzxxOk.png

https://backpack.tf/item/2991136297

Sales at:

5 (5x)

5.5

6 (7x)

7 (7x)

Going with 5-7.