Oh when oh when will "ebay completed sales", with no caveat or context in sight, stop being the automatic answer to this oft asked question?
Ebay is a wild, wooly wilderness of vast cosmic complexity. If you only go by completed sale prices of raw books without a deep and thorough inquisition of the actual facts present in each listing, enlisting the aid of your time honed comic book grading skills and some market knowledge concerning the comic book in question, then you are going to have a bad time.
eBay completed sales, while not entirely useless, are quite nearly so on the sheer face of them.
Of course if you CAN grade, and have handy bookmarks to several of the more popular/reputable dealer websites for comparison purposes, then ebay completed sales can be a fairly handy tool in your quest to avoid spending way too much on much too little!
I really like it when a book is auctioned by an inexperienced seller and sells for ten percent of what a comparable book would have sold for either as a buy it now listing or in an auction by a more experienced seller. That can really throw a wrench in things. I feel bad for the seller when I see those listings. And I feel bad for me if it was a book I'd want and I missed the listing. ughgh. UGHGH