If it can be of of help, I bought in China a couple of 6-speed Boardwalk-style Dahons, the first one for about $110 and the second for $170. The price slipped because of the fall in the value of the dollar against yuan and because of a slight inflation in the Chinese market, eating up in the end the deterioration in the real value of $. With the above, $175 asked for a used single-speed seems quite stiff.

My overall impression of these bikes is that they rely on genuine Dahon components for folding. However, the frames are made by some licensed manufacturers and the remaining components are of a lower quality than on Dahons made for the US market. (I have not owned, though rode, a Dahon made for the US, so cannot express firm opinions.) Within the Chinese market there are still plenty of bikes of a lower quality, though the market is perpetually moving up. For me, these bikes were OK because I needed folders for an occasional use at a location that we occasionally frequent. An excessive investment just did not make sense. They ride OK, but the bikes of better quality are more fun to ride. For a kid who may or may not catch the bug of riding, it may be OK but I would negotiate a substantially lower price.