If I ever say I'm never scared, you know I mean it.

https://backpack.tf/item/996512031

Sale 1) Sold to a bot for 10 Keys + 9 Refined

https://backpack.tf/profiles/76561198307048774#!/compare/1534723200/1534896000

Sale 2) Quicksold for 11 Keys

https://backpack.tf/profiles/76561198810134695#!/compare/1534896000/1534982400

https://backpack.tf/item/3454829259

Sale 3) ?

https://backpack.tf/profiles/76561198048995563#!/compare/1539734400/1539820800

Sale 4) ?

https://backpack.tf/profiles/76561198068064085#!/compare/1539907200/1540080000

Sale 5) Probably 12 Keys

https://backpack.tf/profiles/76561198394877897#!/compare/1540339200/1540425600

https://backpack.tf/profiles/76561198441718422#!/compare/1540425600/1540512000

https://backpack.tf/item/2750581472

Sale 6) ?

https://backpack.tf/profiles/76561198024867201#!/compare/1536105600/1536192000

https://backpack.tf/profiles/76561198053727332#!/compare/1535846400/1536192000

Sale 7) ?

https://backpack.tf/profiles/76561198053727332#!/compare/1536710400/1536969600

Sale 8) ?

https://backpack.tf/profiles/76561198337734785#!/compare/1537142400/1537228800

https://backpack.tf/profiles/76561198122995945#!/compare/1537142400/1537488000

Sale 9) ?

https://backpack.tf/profiles/76561198122995945#!/compare/1537488000/1537574400

https://backpack.tf/profiles/76561198315334238#!/compare/1537488000/1537574400

Sale 10) Sold for a Searing Plasma Buckaroos Hat (14 Keys)

https://backpack.tf/profiles/76561198315334238#!/compare/1537488000/1537574400

https://backpack.tf/profiles/76561198059385185#!/compare/1537488000/1537574400

Sale 11) Sold for 14 Keys

https://backpack.tf/profiles/76561198059385185#!/compare/1538265600/1538352000

IDs match.

https://backpack.tf/item/717426595

Sale 12) Sold to a bot for 10 Keys + 9 Refined

https://backpack.tf/profiles/76561198136254451#!/compare/1533254400/1533340800

Sale 13) Sold for 11 Keys

https://backpack.tf/profiles/76561198381033764#!/compare/1534550400/1534636800 - Buyer's Backpack

Sale 14) Sold + ~1 Key of Items for a Searing Plasma Larrikin Robin (13.5 Keys)

https://backpack.tf/profiles/76561198381033764#!/compare/1534550400/1534636800

https://backpack.tf/profiles/76561198199950729#!/compare/1534550400/1534636800

13.5 - 1 = 12.5, which rounds to 13 Keys

Robin Mini

https://backpack.tf/suggestion/5bd884dd44325a074968992a - 13.5 Keys

Sale 15) Sold for a Dead Presidents Copper's Hard Top?

https://backpack.tf/profiles/76561198199950729#!/compare/1534636800/1534723200

https://backpack.tf/profiles/76561198254918432#!/compare/1534550400/1534723200

Low outlier.

Sale 16) Sold + 2.5 Keys of Items for a Voltaic Hat Protector Universal Translator + ~0.7 Keys of Items

https://backpack.tf/profiles/76561198254918432#!/compare/1537142400/1537228800

https://backpack.tf/profiles/76561198400838979#!/compare/1537142400/1537228800

High outlier.

Sale 17) Sold for 13 Keys

https://backpack.tf/profiles/76561198305492646#!/compare/1540339200/1540512000

IDs match.

Sale 18) Sold for $26.67 when Keys were ~$1.90 each

https://marketplace.tf/items/439;5;u30

http://manicbot.me/keyprice/?at=2018-08-03

26.67 / 1.9 = 14.03, which rounds to 14 Keys

Sale 19) Sold for $20 when Keys were ~$1.90 each

https://marketplace.tf/items/439;5;u30

http://manicbot.me/keyprice/?at=2018-08-19

Low outlier.

Sale 20) Sold for $20 when Keys were ~$1.76 each

https://marketplace.tf/items/439;5;u30

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key

20 / 1.76 = 11.36 Keys, which rounds to 11 Keys

Sales at: ~9, 10.23, 10.23, 10.53, 11 quicksale, 11, 11.36, 13, 13, 14, 14, 14, ~17

Taking 11 as the low end with the numerous sales at or lower than 11 supporting it being in the range.