Let's try this price suggesting.

First time.

New price: 19-22 keys

Proof:

Sale #1 (1 month)= 19 keys

https://backpack.tf/profiles/76561198126835242#!/compare/1525737600/1525824000

Sold for 19 keys.

Sale #2 (3 weeks)= invalid

https://backpack.tf/profiles/76561198093495779#!/compare/1526083200/1526169600

Bulk.

Sale #3 (fresh)= 19 keys

https://backpack.tf/profiles/76561198095022965#!/compare/1527984000/1528070400

Sold for 19 keys.

Sale #4 (2 weeks)= 22 keys

https://backpack.tf/profiles/76561198155320889#!/compare/1526774400/1527033600

Sold for 22 keys.

Sale #5 (fresh)= invalid

https://backpack.tf/profiles/76561198111049983#!/compare/1527638400/1527724800

Bulk.

Relatively young sellers at 20-21 keys

https://imgur.com/a/fSCFYT6

_________________________________________________________

SUMMARY

Sales:

19 x2

22 x1

Going with 19-22 keys.

Feel free to add proof to support or counter my range.