Whether you're a buyer or a seller, the prices that items fetch on eBay are all a matter of timing--more specifically who is looking to buy when an item is listed.

The coin you see below is a good example. In 1975 I was working as a mailroom clerk in a local bank and one of my duties was to roll coin. I found close to 100 of the error coins you see below in a bag of newly minted cents. I bought them and have sold a few over the years, most recently on eBay. I've probably sold at least a dozen over the past year.

The prices that they normally bring have ranged from the low $30 range to the mid $70's. However, one that sold this morning went for $103. And, the condition of this coin is not nearly as nice as some that sold earlier for $35.

It all just depends on who is bidding when an item is listed and whether there is another competitive bidder during the same time period.