it happens quite a bit. but not all the time. some sellers just get lucky. remember that top routed vintage sg that jack was watching, hacked up wiring, non original parts, the least desirable model sg ever built and a really ugly brown color and it went for like twice the value of one in pristine condition.
there are alot of deals on ebay, there are also alot of things with a rediculous reserve and there are a few suckers too.
reminds me of my brother, he made quite a bit of money buying parts cars, mostly 70's and 80's camaro's and trans am's. he'd strip them of all the usable parts like tail lights and dashboards and seats and junk the car. these are some of the least desirable years of cars ever built but there is a certain market of hobbyist who want parts for them, it has become too expensive too build a more desirable car. you can buy a whole car roting in someones yard for $500. then sell the tail lights for $200 to a guy who needs 'em for a smokey and the bandit or kit from night rider look alike or whatever it happens to be.