https://marketplace.tf/items/tf2/31094;5;u134

Two sales in the last week of March, both sold for $146.67

Keys sold at $1.68 both days.

146.67 / 1.68 = 87.5 keys

One other sale, though I can't verify with dates being stretched on the compare link:

https://backpack.tf/profiles/76561198433597251#!/compare/1581379200/1582588800

Sold w/ Aces High Cold Killer for a Fifth Dimension Bat Hat.

150 keys - 15 keys = 135 keys

There's also one seller with a B/O of 70 keys currently, though these things change...

http://puu.sh/FvkkC/d2cb20e53d.png

Personally, I would consider the higher sale, and the lower b/o both outliers to the other two sales:

70 keys (B/O, not sold yet.)

87.5 keys

87.5 keys

135 keys (Outlier)

I'm gonna take the median on this one currently, and say it sits at 87 keys.

Let me know if you think differently!