The values displayed on this site aim to reflect a common trading point in pure, and the best way to get that for a hat is by means of pure sales, which is why they typically weigh strongest. If a hat actually quicksells or if one pure sale is significantly below all other sales, then they can be excluded as low outliers.

However, in this case, there are two such sales, and at least one of them was definitely no QS (it was relisted several times, unsuccesful at 100 for quite a long time).

For the same reason as mentioned above, a sell order at 100 is supportive for a drop as shown here, since it shows that you can currently get this hat for 100 pure. Higher offers support the range as listed here, as they indicate that this can sell over a buyout of 100. But there too we have to realize that we're after a common trading point in pure: if you're asking 100 and reject offers of ~140, it usually means the ~140 in hats that were offered aren't really worth that much in pure, as in that case, the offerer would've just sold his hats for 100 pure and offered that instead, or the offer would've been accepted and the contents resold for 100 keys. (not a hard fact of course, but it's usually an indication).

Evidently, that sell order does not mean it's impossible to get more than 100, and it has definitely not been listed long enough to be a hard cutoff, hence it is used as supportive. The range here reflects what you can get for this hat in pure consistently (low end) and what you can get in decent hats if you're more patient or open in the kind of offers you're willing to take (high end).