I sold my 16gb for $504, and 3 8gb for $305 (dented back), $406 (year old) and $455 (couple weeks old).
I sold the 8gb for my friends. I bough myself an 8 gb for $300 last week since I was tired of using a nokia. I thought I could go til July 11 but I couldnt.
I got $380 for my 10-month-old 8GB iPhone on eBay this past Tuesday. Not a bad deal, as I used my $100 Apple Store Credit towards the purchase of my new 16GB Black iPhone 3G.
$380 (Old iPhone) - $299 (New iPhone 3G) + $100 (Apple Store Credit) = $181 total profit
-$600 (old iPhone)=$419 spent on iPhone
still not bad though