Sale 1:

Sold with Collector’s Spec. KS Tomislav (6) for DBD Baker Boy (Suggestion at 27) + Australium Tomislav (11)

http://www.tf2outpost.com/trade/29332247 - No Outpost

Seller: https://backpack.tf/profiles/76561198132226518#!/compare/1503792000/1503878400

Buyer: https://backpack.tf/profiles/76561198338452906#!/compare/1503878400/1503964800

X = 32

Sale 2:

Sold for $59.99 on Marketplace.tf

https://marketplace.tf/items/614;5;u30

https://backpack.tf/item/751543750

59.99/1.95 = ~30.8

X = 31

Sale 3:

Sold with ~1 key in items for Blizzardy Storm Nanobalaclava (Suggestion at 9.5) + Infernal Smoke Buy a Life (19) + ~1 key in items

No outpost

Seller: https://backpack.tf/profiles/76561198121518467#!/compare/1505520000/1505606400

Buyer: https://backpack.tf/profiles/76561198366562680#!/compare/1505520000/1505606400

X = 29

Sale 4:

Sold for 29 keys

http://www.tf2outpost.com/trade/29365164 - No B/O

Seller: https://backpack.tf/profiles/76561198192602363#!/compare/1505779200/1505865600

Buyer: https://backpack.tf/profiles/76561198079291517#!/compare/1505692800/1505865600

X = 29

Sale 5:

Sold with a key for Dead Presidents Rimmed Raincatcher (Suggestion at 14) + Kill-a-Watt Airdog (Suggestion at 14)

http://www.tf2outpost.com/trade/29369089 - B/O of 28

Seller: https://backpack.tf/profiles/76561198232041512#!/compare/1505433600/1505520000

Buyer: https://backpack.tf/profiles/76561198121518467#!/compare/1505347200/1505520000

X = 28

Sale 6:

Sold for Orbiting Fire Brown Bomber (26)

No outpost

Seller: https://backpack.tf/profiles/76561198366562680#!/compare/1505606400/1505692800

Buyer: https://backpack.tf/profiles/76561198098474556#!/compare/1505520000/1505692800

X = 26

Sale 7:

Sold for Orbiting Fire Pencil Pusher (25)

No outpost

Seller: https://backpack.tf/profiles/76561198337244899#!/compare/1505001600/1505088000

Buyer: https://backpack.tf/profiles/76561198232041512#!/compare/1505001600/1505088000

X = 25

Sale 8:

Sold for 23 keys + 13 ref

http://www.tf2outpost.com/trade/29389021 - B/O of 24

Seller: https://backpack.tf/profiles/76561198341969000#!/compare/1507334400/1507420800

Buyer: https://backpack.tf/profiles/76561198124513061#!/compare/1507420800/1507593600

X = 23

Sale 9:

Sold for 23 keys

http://www.tf2outpost.com/trade/29361465 - B/O of 24

Seller: https://backpack.tf/profiles/76561198112279227#!/compare/1505347200/1505433600

Buyer: https://backpack.tf/profiles/76561198079291517#!/compare/1505260800/1505433600

X = 23

Sale 10:

Sold for 20 keys + 4 ref in ~3 days

No outpost

Seller: https://backpack.tf/profiles/76561198259739195#!/compare/1506988800/1507075200

Buyer: https://backpack.tf/profiles/76561198318847306#!/compare/1506902400/1506988800

X = 20

Sale 11:

Sold with 3 keys + ~0.5 keys in metal/items for Spec. KS Aussie Sniper Rifle (~23.5)

No outpost

Seller: https://backpack.tf/profiles/76561198318847306#!/compare/1506988800/1507075200

Buyer: https://backpack.tf/profiles/76561198348421971#!/compare/1506988800/1507075200

X = 20

Sale 12:

Sold with a bunch of items for Pro. KS Aussie Scattergun

Seller: https://backpack.tf/profiles/76561198348421971#!/compare/1507161600/1507248000

Buyer: https://backpack.tf/profiles/76561198087494715#!/compare/1507161600/1507248000

Not gonna bother with getting an exact value from this sale.

Sale 13:

Sold with a couple keys for Terror-Watt Well-Rounded Rifleman

Seller: https://backpack.tf/profiles/76561198337583821#!/compare/1504828800/1504915200

Buyer: https://backpack.tf/profiles/76561198337244899#!/compare/1504828800/1504915200

Should be/is being used on the Rifleman.

Sale 14:

Sold for Flaming Lantern Larrikin Robin

Seller: https://backpack.tf/profiles/76561198128553858#!/compare/1502668800/1502755200

Buyer: https://backpack.tf/profiles/76561198015384426#!/compare/1502668800/1502755200

Was used on the Robin.

Sale 15:

Bulk for Burning Brain-Warming Wear

Seller: https://backpack.tf/profiles/76561198063271935#!/compare/1502755200/1502841600

Buyer: https://backpack.tf/profiles/76561198132226518#!/compare/1502755200/1502841600

Sale 16:

Bulk for Neutron Star Crones Dome

Seller: https://backpack.tf/profiles/76561198164011243#!/compare/1506816000/1506988800

Buyer: https://backpack.tf/profiles/76561198156255538#!/compare/1506729600/1506816000

Sale 17:

Bulk for Burning Brigade Helm

Seller: https://backpack.tf/profiles/76561198070880686#!/compare/1501891200/1501977600

Buyer: https://backpack.tf/profiles/76561198170090965#!/compare/1501891200/1501977600

Sale 18:

Bulk for Dapper stuff

Seller: https://backpack.tf/profiles/76561198174203179#!/compare/1506556800/1506643200

Buyer: https://backpack.tf/profiles/76561198259739195#!/compare/1506556800/1506643200

Dead Presidents Rimmed Raincatcher:

https://backpack.tf/suggestion/59e0412dcf6c7517e865237d

Blizzardy Storm Nano:

https://backpack.tf/suggestion/59e0726dcf6c752cc6447594

Kill-a-Watt Airdog:

https://backpack.tf/suggestion/59e068cacf6c7511d412b602

Sellers:

21 keys:

https://i.imgur.com/wGXf1MM.png - 16 days

24 keys:

https://i.imgur.com/O4xAhFK.png - 17 days (2x)

29 keys:

https://i.imgur.com/uCruLpk.png - 12 days

30 keys:

http://www.tf2outpost.com/trade/28841795 - 6 months

Sales at:

20 (2x)

23 (2x)

25

26

28

29 (2x)

31

32

6-month old seller at 30 shows that it cannot sell for 30. Excluding 31 and 32.

Going with 20-29, I guess…