I've found that past sales on eBay & ACK are reliable sources for pricing but, as with most things, you have to use your common sense in determining what the current FMV of a knife really is.
For example, you need to make sure that the sales are "recent" (w/in 3 months is best) &, if there is a wide variation in sale pricing, I'd throw out the high & low & pick something in the middle.
Older sales (only ACK provides them, eBay doesn't) can still be a reliable basis for pricing IF the knife is obscure but the pricing of older popular/high demand knives is probably unreliable.
For older sales, sales you also need to account for inflation & "demand" but also need to be able to discount for "greed." No need to worry IMO about ACK's 25% seller fee or eBay's or PayPal's fees in terms of pricing.
A knife will only sell what a willing buyer is willing to pay (fees, sales taxes & shipping included). I personally will only pay or offer to pay a price that includes all additional costs that do not exceed what I think is equal to or less than its FMV.
Most buyers on both sites aren't STUPID. They won't pay anything for a knife & you can see that by how many overpriced knives languish on both sites. The same thing happens here on the BF Exchange.
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That said, IMO the BF Exchange is NOT a reliable source for FMV pricing. If anything most knives on BF go well BELOW FMV & the actual sales prices are almost NEVER publicly posted here.
Just because a seller lists a knife for a specific price here, doesn't mean that's what it sells for that amount. It might & then again it might not. So, listed (and undeleted) pricing on the BF Exchange is only an "indication" of what price the knife might have sold for.
The only exception would a a clear "I'll take it" for an undeleted asking price for a knife, examples of which are few & far between. On the other hand, unless a private offer has been made/accepted, you'll always know exactly what a knife has sold for on eBay. Same on ACK.
It would be "nice" if that was possible here on BF too but as Blues has already mentioned wishing for that is just pissing in the wind.
