It's almost impossible to find a specific ponies value at any given point; prices fluxate at the drop of a hat. UK Exclusives used to be extremely rare and sought after and now they are just as easily accessable as any US released pony.

Keep an eye on ebay auctions, both current and completed. You can also check out the Price Check Archives on the MLP Arena. If the item you're looking for isn't listed, you can start a new thread and the community will more than likely provide you with the information.

The Ebay report used to be the best guide to ebay listings, but hasn't been updated in years. Probably because the amount of MLP ebay listings has skyrocketted since the new my little pony release in 2003. It contained an archive of all closed auctions listed under each particular pony. Everything from commons, to mail orders to the extremely hard to find pony. It was a thorough and mostly accurate way to tell how much your pony might have been worth. Even though it's inactiver, I've included it just in case it's ever updated again. It's also interesting to see what prices ponies used to go for. And you can kick yourself for not getting that $40.00 Mimic way back when!