The hard and fast rule for folding bikes is: you will get what you pay for. Folding bikes are not like ordinary bikes. They have additional technology which must be figured into the cost. Ask yourself this: a sub-$200 regular bike is already a dangerous, low-quality thing. So if a folding bike costs less than $200, what MORE did they skimp on in order to get to that price level?

Even if I was destitute, I would not buy any folding bike that cost less than $400. Below that price level, you should be buying a regular bike (and hesitantly at that).

As to weight limits: claims by vendors on ebay are outright lies. The only bike worth your time in your list is the Dahon. And if you're looking at a Dahon, talk to Thor instead, who will treat you much better than any ebay reseller.