A few notes.

First of all, your first and second sales are for the Strange version, and this hat does not have a strangifier. That means the Strange version should be priced separately, and they should not be used here.

The seller for 50 did sell: https://backpack.tf/profiles/76561198337734785#!/compare/1519689600/1519776000 - 40 matching keys, which is just above quickbuyer price, and I'm not confident that compare is showing the whole sale given the discrepancy between his asking price and additional purchases he made later that day.

However, it also re-sold again, for: https://backpack.tf/profiles/76561198157631229#!/compare/1519776000/1519862400 + https://backpack.tf/item/4803896033 - 21 pure and a P Fetti Executioner, which they quicksold

P. Fetti Executioner mini:

Executioner mini: https://backpack.tf/profiles/76561198021272428#!/compare/1514678400/1514764800 - 28 pure

+

https://backpack.tf/profiles/76561198123288580#!/compare/1517356800/1519171200 - 25 pure

Sellers at 27 and 29 further support that this is pretty much where the market for the Executioner is atm, so taking 26.5. Leaves the Exe + pure sale at ~48. It pretty much supports your current low end, and coincidentally, your high end is off by 2 keys as well since you didn't note two keys of sweets in your calculations. 50-70 is actually appropriate on average, even if it is a bit excessively rounded. Calling it close enough.