Not sure here. Perhaps the range is wide enough that you have captured the value. But your two sales are problematic to me:

http://www.tf2outpost.com/trade/15378213 - sale setting the low end sold the same day - hardly enough time on a mid-high tier halloween hat

http://www.tf2outpost.com/trade/13925022 - sale setting the high end is higher than the b/o. Shouldn't be valued more than 8 anyways - anything more than 8 is by definition unusual overpay

It would be helpful to set prices on one or two of those other hats to help price this. But again, perhaps your range is wide enough on either end that you've captured its value. I'd like to see what another mod thinks.