I've been fairly lucky with lens purchases on E-bay, but I do know what my limits are. More than a couple of times, I've noticed a lens creep up closer and closer to the price of a new one. No thanks, I'll buy through B&H or Canoga.
I did get a Tamron 90mm Macro for a steal. Of course it didn't help that the person posting the lens misspelled the name. As it is with everything else, it's buyer beware.


