Real estate comps are a local market valuation tool.
A house in Irwin, Idaho, is not going to be comped with a house in Lexington, Virginia.
The gun market is much more nationalized than real estate, certainly. But there is still local market to factor in, and Gunbroker often only represents prices seen in more expensive markets.
Case in point: Where I live, you don't see bolt-action shotguns. People just don't own them here, which means they don't come up for sale.
A good condition, complete, run of the mill, bolt action shotgun can be priced and sold here for $150-200.
Yet, if you drop into a gun shop in Georgia, Florida, or South Carolina, they can't move the things with a $75 price tag on them. Many of the shops won't even buy them any more.
On Gunbroker, the bolt action shotguns that do sell are typically going for 40-50% (or more) over sticker prices that you'll see in the south.
One Mossberg 395 that sells for $165 on Gunbroker, to some idiot in The Valley above the Plain (who may not be a total idiot and might have been after the magazine and a some spare parts) is not representative of what a seller is likely to get in Athens, GA, or Gainesville, FL.
Hi-Powers fall into a different category, but it has similar issues. Here, for example, a fixed sight, plain Jane Hi-Power is generally going to be purchased as a tool. It won't sell for as much as it would in, say, Minneapolis, where it is mostly a toy.
But pull out a target sight model, and things change. You suddenly get into the territory of toys and Farm Auction guns*, which will bring a higher price (beyond the normal markup for a target model).
Gunbroker pricing doesn't represent all the nuances and influence of local markets. GB auctions are singularities, showing the result of two (or more) idiots that got in a fight over a particular firearm, at a single moment in time, from unknown markets that likely don't represent your own.
*(Like BBQ guns. For dressing up and showing off, but not as fancy as BBQ guns.)