Bluebook for used tech? ...and, did I get hosed?

[fifield]

I purchased a Dell Inspiron 6000, 512, 1.7, 40 (but I've got a 500 ext.), 15.4wide, 1200x800, for $475 from a loan shark who claimed he is "only makin' fifty dollars (by selling the laptop to me @ this price)" and that I was getting a steal. I knew he was lying about that, but the price seemed fair anyway, so I bought it. However, I've grown increasingly suspicious that I've been hosed by this dude, so I've done some research: orig. price on this unit (late '05-early '06) was prob $875-$1000 depending on exact date purchased and discounts, and among comparable units, mine seems to be on the high end of the current range. I would just like to avoid getting ripped in the future (did I get ripped off, here, though, do you think?), so,

is there any service that frequently updates the fair market value of used technology, especially comps?

If my answer is an obvious google search away, just point it out to me, please, I of course searched there, first, didn't find anything useful. Also, please rate my purchase so I can get a grasp on my standing in this deal.

Thanks!

[Witzo]

I know it sounds lame but the best way to find the FAIR value of any item is Ebay. Look at completed auctions and see what people were willing to pay for comparable rigs.
a Dell inspirion 6000 with no working monitor went for $175 just recently.
You can find generic new laptops at Bestbuy with better specs for the $500 so I wouldn't have purchased it myself.