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eBay is probably the best place to look for. Mac2Sell isn't very accurate IMO as real world prices may fluctuate while Mac2Sell's price remains the same. It should give you some direction though
 
I would check craigslist.

...or you could check your local hood. I had a guy in the TL in SF around the corner from the Apple store try to sell me one for $200.
 
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