If you look at any category of pentax zoom lenses in the data base here (FA or older), pretty much every category has a dog or 2. With some brands (like kalimar) the ratio might be reversed with a few winners and a lot of average and dog lenses, but many of these off brands have a few good ones. Some like sears seem to be a little heavier on the winners than some too (which unfortunately people are realizing and they can sometimes go a bit high on ebay). I'm just glad there are still a lot of unappreciated brands and good lenses can sometimes be had dirt cheap. I can buy 3 or 4 cheap lenses and if only 1 turns out very good, its still a lot cheaper than just buying 1 known good lens. I would hope for better odds than that but I tend to dig up whatever info I can before buying so my odds have been higher than 1 out of 4.
Something else to consider is sample variation. Some lenses are considered lesser quality because they have poorer quality control. Some of those lenses may be very good and others not so good, within the same model lens. Still, if the price is cheap enough, you can end up with some very good ones and the gamble is well worth it. You can also recoup some of your money selling the ones you don't like. Maybe that is why some here buy and sell so many (picking out the good ones to keep).
Last edited by ripit; 09-25-2011 at 05:34 PM.