New Editted Suggestion to also include Xergoyf's research. After narrowing it down, 21-25 Keys is the more likely, accurate range for the taunt.

Past 30 days https://gladiator.tf/sales?item=Nether+Wisps+Taunt%3A+Conga

1 @ 18 Keys

3 @ 21 Keys

1 @ 25 Keys

Previous Month https://gladiator.tf/sales?item=Nether+Wisps+Taunt%3A+Conga&at=2021-12-10T16:02:56.357Z

1 @ 17 Keys 24 Ref

2 @ 24 Keys

1 @ 27 Keys

[Xergoyf's addition]

January

https://gladiator.tf/sales?item=Nether%20Wisps%20Taunt:%20Conga&at=2022-02-11T20:43:02.646Z

1x buy @ 21

February

https://gladiator.tf/sales?item=Nether%20Wisps%20Taunt:%20Conga&at=2022-03-11T20:43:02.646Z

3x buy @ ~21.5

1x sale @ ~23.5

March

https://gladiator.tf/sales?item=Nether%20Wisps%20Taunt:%20Conga&at=2022-04-11T20:43:02.646Z

1x sale @ 30

Compare for the 25 pure sale

https://backpack.tf/profiles/76561199127652476#!/compare/1639785600/1639872000

We have sales at:

17

18 (x3)

21 (x7)

24 (x3)

25