Blanket statements often cover things they shouldn't. In this case, a careful buyer can get some really good deals. I know I certainly did.
Aside from a couple stripped or loose screws, both buggies I purchased on this site performed quite well. I had more damages on my first (purchased new a bit ago) buggy than on the other two combined. Of course my first buggy eats shocks like they are candy...so this was no surprise, and I came prepared.
BUT you are right in the fact that a careless consumer can end up with all kinds of issues. That is why I put forth my thoughts on how you might be able to avoid the nightmares.