Sale 1: Use there.

Sold With 1 Key For Smoking Starboard Crusader.

https://backpack.tf/profiles/76561198283051944#!/compare/1555027200/1555286400

Sale 2: Quick sold for 20 keys.

https://backpack.tf/profiles/76561198039731024#!/compare/1555372800/1555459200

https://backpack.tf/profiles/76561198044684270#!/compare/1555372800/1555459200

Sale 3: ~24 Keys Pure.

https://backpack.tf/profiles/76561198080179568#!/compare/1557619200/1557705600

https://imgur.com/a/hgTvbSu

Sale 4: ~24 Keys Pure.

https://backpack.tf/profiles/76561198080179568#!/compare/1553472000/1553558400

https://backpack.tf/profiles/76561198227657840#!/compare/1553558400/1553644800

Sale 5: ~22 Keys Pure.

https://backpack.tf/profiles/76561198227657840#!/compare/1553817600/1554076800

https://backpack.tf/profiles/76561198349886701#!/compare/1554076800/1554163200

Sale 6: Untrace.

https://backpack.tf/profiles/76561198349886701#!/compare/1555027200/1555113600

https://backpack.tf/profiles/76561198415484830#!/compare/1555027200/1555113600

Sale 7: Untrace.

https://backpack.tf/profiles/76561198415484830#!/compare/1555286400/1555372800

https://backpack.tf/profiles/76561198002757046#!/compare/1555286400/1555372800

Sale 8: ~22 Keys?

https://backpack.tf/profiles/76561198002757046#!/compare/1556582400/1556668800

https://backpack.tf/profiles/76561198289062324#!/compare/1556582400/1556668800

Sale 9: Untrace.

https://backpack.tf/profiles/76561198289062324#!/compare/1556668800/1556755200

https://backpack.tf/profiles/76561198387159963#!/compare/1556409600/1556755200

Sale 10: Untrace.

https://backpack.tf/profiles/76561198387159963#!/compare/1556755200/1557014400

https://backpack.tf/profiles/76561198826771573#!/compare/1556755200/1556841600

Sale 11: ~20 Keys? (QS)

https://backpack.tf/profiles/76561198119634686#!/compare/1556755200/1556841600

https://backpack.tf/profiles/76561198826771573#!/compare/1556755200/1556841600

Sale 12: ~23 Keys Pure.

https://backpack.tf/profiles/76561198119634686#!/compare/1557878400/1557964800

https://backpack.tf/profiles/76561198121944933#!/compare/1557792000/1557964800

Sale 13: Untrace. (Probably QS)

https://backpack.tf/profiles/76561198071415643#!/compare/1555113600/1555200000

https://backpack.tf/profiles/76561198080179568#!/compare/1555027200/1555113600

Sale 14: ~22 Keys Pure.

https://backpack.tf/profiles/76561198080179568#!/compare/1556755200/1556841600

https://backpack.tf/profiles/76561197997339757#!/compare/1556668800/1556841600

Marketplace.tf Sale:

https://marketplace.tf/items/30173;5;u62

Sale 15: ~30 Keys.

May 17

$59.99 / 1.83 = 32.78 keys

https://bot.tf/stats/listings/MVDPNGVM

Sales: 20/20/22/22/22/23/24/24/30

Going With 22-30 Keys.

Thanks to scourge for the premium!