Is eBay really the best place to buy old lenses?

Just a thought, I'm getting a D90 and looking to buy a few lenses to go with this. I'm looking to take advantage of the focus motor and hopefully get some cheap, but good quality autofocus older Nikkor or alternatives. Ebay seems to be the place with the best choice, but having a look, what about places like MBP photographic, Ffordes, Grays etc? Are these just as good?

Ultimately, I'm asking where the best place to find a cheap, good quality autofocus lens that is a bit older.
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