Unfortunately, we can't make hard and fast rules about things like this. Every situation is different. Consider all the circumstances here. The seller of the hard top never had an outpost trade. Almost always this means that he was the one who offered it on the pug.

As Marty indicates above, the point of overpay is to determine the pure equivalent value on a hat. If a hat sells in a day at 30 keys in pure, it probably shouldn't get valued at less than 30. If it takes a week to sell for 30 keys, then it probably shouldn't be considered a pure equivalent. This doesn't matter if there was a previously accepted suggestion or not. Now, we can't make suggesters look at previous suggestions. This sort of debate is a higher order one that we leave for experienced suggesters, and we leave decisions like these to the experienced suggester. For everyone else, applying overpay is just the easy way (though not always the right way) to do things.

That's verbose. To make it simple, when in doubt, apply overpay. If no overpay is applied, you must provide justification. It's at the discretion of the suggester and the moderator assessing the suggestion whether the justification is appropriate.