I had 3 pairs of Polaroid in this price range (40-50€). Generally, their thing is that they have good lenses with a bad frame. The plastic is that of the noname fake glasses of 10 euros. It could be of better quality. Maybe the more expensive ones are more carefully made.
With this particular pair, I had a problem, it reflected sometimes in the center of the lens. It has never happened to me with any other pair, but it is also subjective. I lost them in Rome. I didn't feel sad at all.