I've had good luck buying them from rental places. I got my last 12' dump from some rental place for a pretty decent price. The rental ones are nice because they are very heavy duty compared to a lot of the crap out there, I bet it weighs double what our light duty one is.
To the guys using 16's and bigger: how do you manage in the big cities, there are times where we can barely fit our 12' in the yard/on the street. I would love to get a 16 or a 20 but I'm afraid I wouldn't be able to navigate some of the alley ways.