I live near two camera stores, one sells extremely cheap filters under $10 and work fine on cheap glass, when i started buying good glass from them they remembered I was a long time customer and said don't use the old UV filters not here lens, I was expecting an up sale they pulled out a few offerings, i think HOYA HMC and the one in the black box, I didn't grab them thinking it would be cheaper on amazon but they were actually cheaper.
Another vendor is right down the street, they sell filters for about 30% over list, a quick phone search made me real uneasy over the heavy markup, i love supporting mom and pop but not keeping mom and pop in caviar taste. I once needed a lens in a pinch and the salesman just grabbed the filter and scanned it and gave me the total, when I asked how much for the filter he said " i can't let you put something cheap in front of this good glass" while he was pushing a good filter it was overpriced and I said I would rather put nothing than over pay, they wouldn't price meet and I moved on.
They push promaster and mark it up, I don't know this for a fact but I know have a friend who deals in wholesale and told me promaster is marked up insane, while i can't speak on quality I hear its no different than the $5 vivitar you can find.
I was always concerned with filters but now I would prefer none with a hood if I wasn't getting a good deal on a nice filter.
I personally wish (i know canon sells UV filters but i read terrible things?) the lens would come with a UV filter and have the whole thing included, i like the idea of the extra protection and just screw off and replace. i know that wont happen thought....