that is a good point I wondered about also...... does it still have the other regular blade head with it also.
maybe the cutter got pitch on the cutters and they rotated instead of cleaning them
I could think of several reasons: 1) not familiar with the wear characteristics of carbide inserts OR 2) one or more cutters got knicked from striking an embedded nail or other similar event (which will do no damage to the actual jointers, just the knives).
But Tat is absolutely correct that you will seldom find an 8" jointer, of any sort, for anywhere near the price that many may be used to on the used market when viewing 6" jointers. The reality is that brand new an 8" jointer sells for 50-100% (typically around $1200+) more than its 6" little brother and because of their relative scarcity on the used market the 8" jointers fair much better and retain much of their original value if they were well maintained during their lifetime.
I would never discourage anyone from trying to talk a price down and securing a better deal, but the reality is that this is a fine jointer, much in the same class as my Jet JJ-8CS (straight knives) but with the added benefit of a helical cutterhead -- it's not like one is likely to come out behind on the deal even at the asking price if one is in the market for an 8" Jointer.
To alleviate any fears of no warranty, simply take a trusted square with you, check that the bed is square to the fence and the cutterhead level to the bed, then ask him to demonstrate jointing a 2" thick board (or thereabouts) and check it for squareness and flatness (for shorter lengths, it should literally seem to "stick" to the jointer bed when you try to lift it straight up if it is flat) using your trusted square -- if everything checks out then you have a good jointer right off, if not then it may need some further adjustment and you can use it as a point to talk the price down further.