Can't price an unusual to save my life, so here goes nothing.

Sale 1: https://backpack.tf/item/6778049221

https://backpack.tf/profiles/76561198061108999#!/compare/1529280000/1529366400

https://backpack.tf/profiles/76561198020918186#!/compare/1528156800/1534464000

Sold for what looks to be like 30 keys pure (screenshot of compare page: https://gyazo.com/4ecdcee185d42e4bdbb6fed8ff1f15d5 )

Item 2: https://backpack.tf/item/6547985729

Followed a dead end for 15 minutes trying to find the sale between Merigold and Breezze, only to realise they're the same person.

Sale 2:

https://backpack.tf/profiles/76561198212216969#!/compare/1532822400/1533945600

https://backpack.tf/profiles/76561198050062763#!/compare/1532563200/1533945600

Incredibly messy, I know, but it's alright because Breezze came through with the clutch and provided a screenshot: https://i.imgur.com/4d5yj3k.png

Now, here's where things get hairy. The following items have been updated in the last three months, and as such, do not need minis:

https://backpack.tf/stats/Unique/Killer%20Exclusive/Tradable/Craftable (https://backpack.tf/item/2234336791) default price is 1.55 ref, but with paint, the bptf suggested price is 18.95 ref, which is what Erik said to go with.

https://backpack.tf/stats/Strange/Toowoomba%20Tunic/Tradable/Craftable (https://backpack.tf/item/6818514830) (30.36 ref)

These ones haven't, and need minis:

https://backpack.tf/stats/Unusual/Full%20Metal%20Drill%20Hat/Tradable/Craftable/56 (https://backpack.tf/item/1781613827)

https://backpack.tf/stats/Strange/Professional%20Killstreak%20Original/Tradable/Craftable (https://backpack.tf/item/1522559419)

https://backpack.tf/stats/Strange/Specialized%20Killstreak%20Jag/Tradable/Craftable (https://backpack.tf/item/1425560149)

https://backpack.tf/stats/Strange/Killstreak%20Rocket%20Launcher/Tradable/Craftable (unable to find item)

https://backpack.tf/stats/Strange/Specialized%20Killstreak%20Scattergun/Tradable/Craftable (unable to find item)

So, here goes. Here are the minis:

Full Metal Drill Hat: https://backpack.tf/suggestion/5b76da37cf6c756c440fe47a (using 14 keys as the mini, even if that suggestion gets closed)

Strange Professional Killstreak Original: https://gyazo.com/9a01fbe3ae340ab8340e78300645bc19 (lowest classified sellers are 15.87 keys. Erik said to go with lowest price on classifieds)

Strange Specialized Killstreak Jag: https://gyazo.com/70e725cf89092311690a72067dd3fb41 (30.66 ref / 0.94 keys)

Strange Killstreak Rocket Launcher: https://gyazo.com/e4efc4f2b7d09102e6f9d844145e653a (22 ref / 0.67 keys)

Strange Specialized Killstreak Scattergun: https://gyazo.com/70964355429713b6c53622bd841cd2e6 (1.61 keys)

All of this, plus 2 keys, gives us a sale of: 14+15.87+0.94+0.67+1.61 = 33.09 keys, or 33.1, or 33, rounded ("for all unusuals above 10 keys, please round to the nearest whole key").

Hence, we can discern a range of 30-33 keys. Please note that there is a sale from Juliαи to Cheerful in one version (https://backpack.tf/item/6547985729), but this is being used in the Green Energy Brain Bucket suggestion as this is acting as the mini for that.

Credit to the following people for their help:

Breezze (https://backpack.tf/u/76561198050062763)

Erik (https://backpack.tf/profiles/76561198091502579)

JoXu (https://backpack.tf/profiles/76561198065425005)