The 35 mixed sale is outdated, as it occurred in late April. As of now, sales older than May 16th cannot be used.

There are a bunch more marketplace.tf sales:

https://marketplace.tf/items/tf2/31028;5;u17

$60 / $1.92 = 31.25 keys

$64.99 / $2.00 = 32.49 keys

$55 / $2.00 = 27.50 keys

--- 3 you had, Key prices varied based on the day so they are not all 35: ---

$69.99 / $1.99 = 35.17 keys

$69.9 / $1.92 = 36.41 keys - https://bot.tf/stats/listings/Y79O116N B/O was 34

$69.99 / $1.84 = 38.04 keys - https://bot.tf/stats/listings/Y9Q81QVX B/O was 34

So sales at:

28

31

32

34 (x2)

35

https://bot.tf/stats/listings/MNRWKDOQ - BooBot has been selling at 34 for 2.5 months, 35 at longer.

I would call 35 high here due to the seller and go 28 - 34 keys here.