Thats just how 3rd party/generic lenses make money. Many are very favorably comparable in quality to name brand lenses, with enough research you can find reviews that back up those claims, and there are a few 3rd party fanboys that lurk forums that will tout their superiority till the end of time. They are also priced to compete with name brand used and refurbished lenses, and always cheaper than the new name brand lenses. When a potential buyer like you is looking for a specific lens, they are always tempted with the dilemma of "hey I can get this off brand lens for just a little more than a used Canon version, and some websites rave over how good this lens is in comparison with the Canon too, so it makes sense to buy the new off brand one right?" The problem comes with holding their value. A decent Canon or Nikon lens always holds its value very well. 3rd party lenses never do, there is no demand for them compared with name brand. None of these lenses are inexpensive, it comes down to wise investment of your money. Buy 3rd party lenses used never new.
thank you very much for this, well said. I've been buying third party lenses used now for a few years and since I've always got them at killer deals, they're resellable without much loss on my part.
I have decided to go with Canon. either the IS or non IS, depending on deals I see, i'll cop either or. thank you again!