Yet another suggestion for the Challenge ;)

Blizzardy Storm Front Runner

Sale 1

https://marketplace.tf/items/760;5;u30

http://manic.tf/keyprice/?at=2018-08-21

Sold for 47$ / 1.90$ = 24.74 keys which rounds to 25 keys

Sale 2

Bulk for a Duped BF Merryweather

https://backpack.tf/profiles/76561198259820488#!/compare/1531958400/1532217600

https://backpack.tf/profiles/76561198112336424#!/compare/1532131200/1532217600

Sale 3

Pretty bulky on both sides

https://backpack.tf/profiles/76561198112336424#!/compare/1532822400/1532908800

https://backpack.tf/profiles/76561198032016356#!/compare/1532822400/1532908800

Sale 4

Untrace and quickly traded away.

https://backpack.tf/profiles/76561198032016356#!/compare/1532908800/1532995200

https://backpack.tf/profiles/76561198418244311#!/compare/1532908800/1532995200

Sale 5

Seems like it sold for 20 pure

https://backpack.tf/profiles/76561198847232953#!/compare/1532995200/1533081600

https://backpack.tf/profiles/76561198091267840#!/compare/1532822400/1533081600

Sale 6

https://backpack.tf/profiles/76561198091267840#!/compare/1533168000/1533254400

https://backpack.tf/profiles/76561198067211253#!/compare/1533168000/1533254400

Sold for a Searing Plasma Brass Bucket (33 keys) + 1 key in adds, seller has traded it away quickly for 23.5 keys as seen in the compare.

Sale would be 34.

Sales: 20 / 25 / 34

34 is a clear outlier here, if it was outdated the 23.5 key resale + the extra key would round it up to 25, supporting the high end.

There are 2 buyers at 17 and one at 13 currently.

Only seller is 5 days old at 25 keys.

Although the 25 key sale was a Marketplace.tf sale, it is supported by the Brass Bucket sale.

I'll go with 20 to 25 keys here.