Hi. I'm with mrblackcat on this.I have a background in property appraisal. Using the median average is where you find true value of an item. I've been on Ebay for a few years. I've tried all different ways to sell on ebay. Auctions occasionally fetch higher than what the item is worth. Though if it gets too high the buyer just doesn't pay-up. If you go though and check Items that sold for really super high (way more than its worth) amount you will find a lot of them where relisted. I'm sure their is shilling going on. People may run on emotions but are not completely stupid. If someone way overspent on am item. Then they will take their lumps from ebay and walk from it.
The best is to sell items as buy it now, or at auction with the starting price close to what it worth. (leave a little on the table to bring in the buyers)
Realize that each item is a market and markets go up and down due to supply and demand. That could be daily, yearly, or by the minute. Trust your comparables when determining values. If the item dose not sell in a few months, than you need to re-evaluate.(If this is going off topic, witch I have a tendency to do. than I apologize.)
hope this helps.