Bored, so I did this.

MP.TF Sales:

https://marketplace.tf/items/31025;5;u35

3x $26.99

May 19th - $26.99 / $1.81 = ~14.9, round to 15

June 15th - $26.99 / $1.84 = ~14.7, round to 15

2x ~$17

May 26th - $17.09 / $1.81 = ~9.4, round to 9.5

May 30th - $17.00 / $1.82 = ~9.3, round to 9.5

Key Prices:

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key

I couldn't find other sales due to the lack of premium, so I'm not sure if MP.TF sales alone will be enough. Let me know your thoughts.