Have no idea, many many times though.
same here. Voted 20 or more.
I don't use Craig's list much, but I have bought and sold stuff on Craig's List.
Clothes, mostly, are the items that we buy at a fraction of the manufacturer's suggested retail price, usually with a combination of sale and coupon. I have a jacket that had a $79 dollar price tag that I got for 11 dollars. I have a winter coat with a $399 price tag that I bought for 75 dollars. Of course, it's always at the end of the season so I always have "last year's" fashions. Everything I'm wearing now except the underwear were bought at less than half the sticker price.
It just takes a combination of patience and timing.
For artesania, souvenirs and trinkets from street vendors it's usually pretty common to negotiate a price that is 50% of the asking price, but I always suspect that the asking price varies greatly depending upon whether you look like a local, a poor foreigner, or a rich foreigner. An Egyptian might ask me for 10 pounds for a lamp that he'd sell to another Egyptian for 5 pounds, so it's not clear whether I should say that I got the lamp for 50% off when I ended up paying 5 pounds.
Electronics, such as keyboards, guitars, toys, and computers, can usually be had for 50% below MSRP if you're not in a hurry and willing to spend some time shopping around. One rule of thumb is: go to the store to try, go on-line to buy. For example, Guitar Center is a great place to practice, but I'd go with musiciansfriend.com when I'm ready to buy.
Things like new cars and new houses are a tougher sell. It's difficult to get more than about 15% off sticker price for a new car, and for a new house it's even tougher because the builder has to get his money back. For used houses you have more wiggle room, but I can't imagine getting one at 50% off list price. Of course, if you're a flipper, looking to buy repossessed houses and foreclosures at auction and put up with the fact that all the copper plumbing has been stolen by the dispossessed previous tennants, then you can get some cheap used houses. I have a friend that bought a small house for 12 thousand, put 15 thousand worth of fixes in, and then sold the place for about 120 thousand. Tidy profit. I have neither the time nor inclination to be a flipper.