You definitely pay for quality. I have Hella 450's for fog and driving lights. My brother in law bought a set of $20 lights at Walmart. They both used the same exact bulb (H-2 or 3 or something like that) but the Hella's blew his away as far as brightness and ligth pattern. If you can foot it go for the quality, stay away from cheap. I have no experience with the PIAA's or other lights so I have nothing to say against them but I swear by Hella's.
I also busted the covers on mine once. Sitting idling in the winter talking to someone and then took off through some real light powdered snow. The sudden cold on the hot lenses cracked them bad. I wrote to Hella asking about ordering new ones and they automatically sent me new lenses for free. Good luck on the $20 ones with that scenario.