We're gonna walk down to Electric Avenue

https://backpack.tf/item/1999831638

Sale 1) Sold for 20 Keys

https://backpack.tf/profiles/76561198078871795#!/compare/1509321600/1509408000 - Seller's Backpack

https://backpack.tf/profiles/76561198150669590#!/compare/1509321600/1509408000 - Buyer's Backpack

19 of these Keys were used to buy the Tesla Coil Rebel Rouser that you see in the Seller's Backpack:

https://backpack.tf/profiles/76561198258728302#!/compare/1509321600/1509408000

https://backpack.tf/item/5997341489

Sale 2) Sold for 18 Keys + 12 Refined

https://backpack.tf/profiles/76561198282372085#!/compare/1509408000/1509494400

Low Outlier.

Sale 3) Sold for a Kill-a-Watt Towering Pillar of Hats (22.5 Keys) + ~0.4 Keys of Items

https://backpack.tf/profiles/76561197963500354#!/compare/1510963200/1511049600

22.5 + 0.4 = 22.9, which rounds to 23 Keys

Sale 4) Sold + ~3 Keys of Items for a Showstopper I See You + ~3 Keys of Items?

https://backpack.tf/profiles/76561198073278326#!/compare/1512259200/1512518400 - Seller's Backpack

https://backpack.tf/profiles/76561198114604882#!/compare/1512432000/1512518400 - Buyer's Backpack

The Sniper Rifle history doesn't match, but comes together with the other items in the Seller's Backpack.

Plus, nothing added with the I See You shows up in the Buyer's Backpack. Either way, I'm not including this sale since the taunt has Sellers under 19 Keys.

Sales 2 and 4 are low because of these buyers: https://imgur.com/a/XZcVP at 19 Keys and above.