Marketplace.tf sales: https://marketplace.tf/items/tf2/1112;5;u3028

June 13 2020: $9.99 (median key price $2, 9.99/2=5 keys)

There are also other sales in April 2020 but they can't be used to price the taunt because they're outdated (over 3 months old)

April 11 2020: $8.99 (median key price: $1.70, 8.99/1.70=5.29 keys)

April 17 2020: $9.95 (median key price: $1.77, 9.95/1.77=5.62 keys)

One recent sale in item histories: https://backpack.tf/item/2802937797

This leads us to the taunt being traded to a Marketplace.tf bot, the name of the owner before the bot is the current seller on the site

Taking 5 keys as the value for my suggestion