I was suffering from gadget lust for a 100-400L when my boss said a mate was selling some canon gear. Turned out he had a 100-400L barely used for £500; very happy with that.
Living in Australia where bargains are as rare as hen's teeth, I did get a 1 year old Sigma 24 f/1.8 for $200 when they are about 4x that new. Not that exciting.
I got a mint condition 80-200 f/2.8L for $550, including case, collar, hood and original box. I used it for about 2-3 years, and sold it for $150 profit.
My best deal is my excellent condition 1Ds Mark II for $1700.
When I first signed up on fredmiranda, one of the more vocal/opinionated members here offered a free 50 f/1.8 II to the first person who could find his telephone number in a recent post and give him a call. I did; he sent the lens.
Canon FL 55 f/1.2 -- $81 (or less).
Got this on Ebay sold 'as is' attached to a working FT (either -QL or -b, don't remember at the moment). Haven't sold the body yet, but when I do, the final cost of the lens will be lower than $81. And it's an incredible lens.
I bought a D300 for $500 brand new including the 18-200 lens.
it was an open box from a retailer and it was in mint condition.
I ended up selling it after playing around with it, to come back to canon.
I got my pristine Pentax LX for $270 CAD with an additional grid focus screen. I could've easily turned around and sold it for 2x what I paid, but instead I'm putting a few rolls of film a week through it and bragging about the deal I got on forums .
I got my Canon 1DMkII for $1100 CAD, which is a decent deal - definitely not as sweet as the LX, though.
.