Why are some items worth more than others? That's the big question isn't it. A pop up R2 is worth a lot more than an Anakin because it has a huge sticker round it that deteriorates with play, Anakin doesn't. It has an accessory that gets lost, Anakin doesn't. And it is a more popular character and more sought after figure. Mostly popularity I think. It seems some items are more consistent and predictable in their value and others can vary wildly which can be seen on Star Wars tracker. Searching for completed listings on ebay for a particular figure or item can be interesting and with surprising results.