I was just searching out a KCNC seatpost - found 2 bike shops who were selling it for $108 + shipping, found it on e-bay at a "buy it now" for $69.95 + 8.99 shipping - made an offer of $60, and got it.
Here's the thing about parts on e-bay - 1st, know exactly what you are looking for - types, size, weight, whatever. 2nd, do your research so you can figure out what a good price is (and don't forget the shipping!) I have found better deals locally or at on line stores than I have on e-bay. 3rd - Once you find what you're looking for at a price you like, read the ad carefully & send the seller an e-mail with any and all questions you might have about thier offering.
If you pay attention to what you're doing, and take the seller's history into consideration, you should have no problems with ebay.
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As with mud, life, too, slides by.