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Watching on eBay makes little sense in reality. The market there is such that two similar items days or weeks apart can end with wildly differing prices. This is particularly true of the less common items.

Nope, basic economics in a diverse market would suggest that as long as the items are listed in exactly the same way they will reach the same price. Bargains can be had when something isn't reaching the correct audience, but otherwise it's a seller's market.

Watching makes sense, know how much your ceiling price is before hand and bid at the last moment.