The situation here is a unique one. Conventionally, we don't cap full pure sales at a lower buyout, but in some cases we do - this depends on the nature of the sale and why extra was paid. For this sale, had the buyer bought the hat on Marketplace, they'd have paid the equivalent of 90 Keys less than they paid in Keys. That cash price was in place for weeks as noted by Moth above, so it holds significance here. While the listing on this site may have stated a different Key price to convert to the number of Keys the seller would want, the fact still remains that any buyer could've paid less with cash on Marketplace.

The rationale given for why the buyer paid more was to avoid dealing with cash, and an argument can be made that the premium paid because of that should be treated like the premium paid for a reservation fee - these are excluded from suggestions because it's a convenience to reserve a sale, but anyone could just as easily pay the buyout price without reserving in advance. On the other hand, with cash not being explicitly pure in the sense that it's not a Key, an argument can be made that the labor needed to convert between cash and Keys is real, and there are risks to dealing with cash, so wanting to trade for a larger value in Keys than in cash is understandable.

After discussing this, we feel it'd be best to make an exception for this specific case and have a range between the lower cash buyout converted to Keys and the actual sale value in Keys (910 - 1000). 910 isn't explicitly a buyout in Keys, but it being so much lower than 1000 and listed for a lengthy period should not be ignored.