Lets go

Sale #1:

https://marketplace.tf/items/tf2/30748;5;u120 ~ Aug 9 ~ 125.99 = https://manic.tf/keyprice/?at=2019-08-09 ~ 68.85 keys (69 keys)

Sale #2:

https://marketplace.tf/items/tf2/30748;5;u120 ~ Aug 2 ~ $92 ~ https://manic.tf/keyprice/?at=2019-08-09 ~ 50.2 keys

Sale #3:

https://marketplace.tf/items/tf2/30748;5;u120 ~ July 31 ~ $92 ~ https://manic.tf/keyprice/?at=2019-07-31 ~ 50.11 keys

Sale #4:

https://backpack.tf/profiles/76561198328984748#!/compare/1567987200/1568073600 ~ 39 keys

Sale #5:

https://backpack.tf/profiles/76561198126679929#!/compare/1565827200/1566000000 ~ this is around 90 keys.. so probably an outlier

Sale #6:

https://backpack.tf/profiles/76561198281972362#!/compare/1563580800/1563753600 ~ sold for a phantasm jr halogen ~ no mini for it tho

Sale #7:

https://backpack.tf/profiles/76561198047941585#!/compare/1567555200/1567641600 ~ sold for a blizz headsplitter + 12 keys

Mini:

https://backpack.tf/profiles/76561198135388328#!/compare/1568505600/1568592000 ~ bought off scrap.tf for 21 keys (not low sale as seller at 24 for headsplitter on classies anyway)

~ 32

Sale #8:

https://mannco.store/item/12176 ~ 80 / 1.69 = 47.3 keys

Sales at:

32, 39, 47, 50, 50, 69, 90+

Gonna exclude 32 as buyers pretty close. 90 obv outlier and 39 seems low compared to other sales.

Taking 45-70, as suggested by crimson