Current low-end price is based off quickbuyer prices—needs a slight adjustment. Proof was gathered over a 1-week period and I've excluded Grenade Launchers with high-value parts or killstreaks unless it falls within or under the suggested range.

Sold:

http://www.tf2outpost.com/trade/24279228 22 keys (price was adjusted from 24 keys; possible quicksell)

http://www.tf2outpost.com/trade/24252968 23 keys

http://www.tf2outpost.com/trade/24210040 23 keys

http://www.tf2outpost.com/trade/24210040 23 keys

http://www.tf2outpost.com/trade/24273272 23 keys (screenshot: http://i.imgur.com/Qppz7lK.png ; SL was valued at 22 keys)

http://www.tf2outpost.com/trade/24175245 24 keys (screenshot: http://i.imgur.com/duBJSjp.png )

Sellers:

http://www.tf2outpost.com/trade/24227659 24 keys (interested buyer, but with untradable keys)

http://www.tf2outpost.com/trade/24360269 24 keys

http://www.tf2outpost.com/trade/24359587 24 keys

http://www.tf2outpost.com/trade/24353035 24 keys

http://www.tf2outpost.com/trade/24355420 25 keys

http://www.tf2outpost.com/trade/24351793 25 keys

http://www.tf2outpost.com/trade/24180282 25 keys

http://www.tf2outpost.com/trade/24220780 27 keys

http://www.tf2outpost.com/trade/24317929 28 keys

Buyers:

http://www.tf2outpost.com/trade/24123518 18 keys

http://www.tf2outpost.com/trade/23443971 18 keys + 1 ref

http://www.tf2outpost.com/trade/24223103 20 keys

http://www.tf2outpost.com/trade/23830352 20 keys

http://www.tf2outpost.com/trade/24054253 20 keys

http://www.tf2outpost.com/trade/22299327 20 keys

http://www.tf2outpost.com/trade/20881910 21 keys

http://www.tf2outpost.com/trade/21114021 21 keys

http://www.tf2outpost.com/trade/23383934 21 keys

http://www.tf2outpost.com/trade/20685951 22 keys

http://www.tf2outpost.com/trade/24244682 22 keys

http://www.tf2outpost.com/trade/23757693 22 keys

Classifieds:

http://i.imgur.com/3y9ye0M.png

2 x 24 keys

1 x 25 keys

2 x 26 keys

Conclusion:

• 22 keys shouldn't be in the range. Sellers at 22 keys don't appear often or are sold too quickly as well as a few quickbuyers are willing to pay 22 keys.

• 23 keys is where most of the recent sales have occurred.

• 24 keys is the current most available trading point. It should be included because it's possible to sell at 24 keys along with the low availability of sellers at 23 keys. At the time of suggestion I couldn't find any sellers below 24 keys.