Parts ads
Or you find a ad for a part that you need only to discover that the part has been sold long ago and the person who put up the ad is to lazy to take it down
or even better... i saw something that had been up for
months and months and contacted the guy: hey, i know this has been up for a long time. is it still avail and if so would you take [basically about 3/4 of the price]. dude wrote back basically telling me i didn't know **** and i was wasting his time and it was a good deal and that's less than they are in the junk yard, if you can even find them (it wasn't, and you can).
so i thanked him and said that he's got my info if he changes his mind.
i found what i needed a day or so later and the guy that i bought the stuff off of was so thankful that i actually showed up and didn't waste his time wound up knocking enough off so that it was cheaper than the other jerk and then proceeded to load up a bunch of other stuff that he didn't want and thought that i could use for free.
the original guy hit me back weeks later asking if i was still interested, but still had a tone that i didn't like. so i politely informed him that i had procured the pieces i needed thru different avenues, at a better price point and the person was a pleasure to deal with. i further said that he should enjoy the one he had because it was a real nice one, and they're getting harder to find and just going up in price. but if he wanted to sell it still i'd give him 10 bucks and burrito for it.
that went over quite well. oh, and the dude still has it listed up for sale.