Some sales people make commission on what they sell so be prepared for it. If you really want a Nikon, Minolta, or Cannon lens then get one. Try not to let them switch to a product that you did not suggest and might be inferior. Here is a what I typically carry on any given underground photography trip. The craze of on-line auctions is tremendous.
People tend to get intensely caught up in a bidding war ignoring relevant prices.
I have seen it too many times. I have purchased some items on these type auctions but only after I had researched what I could get for somewhere else. This philosophy should be applied to all items, photography related or not. I have watched people bid higher prices for used equipment than it could be purchased for new. All you have to do is call and ask for one.