Marketplace.tf sales: https://marketplace.tf/items/tf2/1112;5;u3029

July 9 2020: Sale at $6.95 (median key price: $1.99, 6.95/1.99=3.49 keys)

July 12 2020: Sale at $10 (median key price: $1.98, 10/1.98=5.05 keys)

August 3 2020: Sale at $9.99 (median key price: $1.89, 9.99/1.89=5.29 keys)

I also found 2 histories of recent sales.

https://backpack.tf/item/2830190939

https://backpack.tf/profiles/76561198248516218#!/compare/1594080000/1596672000

https://backpack.tf/profiles/76561198040380060#!/compare/1591228800/1594598400

This history shows the taunt being sent to a Marketplace.tf bot, but I couldn't trace it's current state

https://backpack.tf/item/7692807587

https://backpack.tf/profiles/76561198799616536#!/compare/1593388800/1596240000

https://backpack.tf/profiles/76561198047445236#!/compare/1593388800/1593993600

Not sure what the sale was here

With the proven sales, taking 3.49-5.29 keys as the value for my suggestion, 3.5-5.3 keys if rounded