Let's try that again!

https://marketplace.tf/items/tf2/30609;5;u3018

JULY 8th @ $13.18 / 1.83 = ~7.202 --> 7.2 keys https://manic.tf/keyprice/?at=2019-07-08

JULY 16th @ $14.23 / 1.82 = ~7.818 --> 7.8 keys https://manic.tf/keyprice/?at=2019-07-16

AUG 3rd @ $15.52 / 1.82 = ~8.52 --> 8.5 keys https://manic.tf/keyprice/?at=2019-08-03

SEP 21st @ $19.99 / 1.82 = ~10.98 --> 11 keys https://manic.tf/keyprice/?at=2019-09-21

https://backpack.tf/profiles/76561198314211872#!/compare/1565913600/1566000000

https://backpack.tf/profiles/76561198046218075#!/compare/1563840000/1566000000

Sold for 6 keys

https://backpack.tf/profiles/76561198314211872#!/compare/1566086400/1566172800

https://backpack.tf/profiles/76561198359251673#!/compare/1566000000/1566172800

?

Conclusion: 6, 7.2, 7.8, 8.5, and 11 keys.

6 is an outlier, sold to buyers and nothing supports it.

Rounding 7.2 to 7 (Thanks Lemons!)

Excluding 11 because previous b/o's were lower (Thanks K1ng!)

Taking 7-8.5