Used parts don't coun't when you're quoting build ups as far as I'm concerned. There are too many variables (parts selection, location, availability, time of season, etc) to give a fair dollar value on specific parts. Two guys with the same set up could end up hundreds...even thousands of dollars apart by the time is all said and done.
For example. My nephew got a sweet deal on a nearly complete used base S-Trim kit a while back....all said and done, he picked it up for $600. I see this same kit being sold elseware used for $1,500-up. That's a pretty big difference in price and a little tough to quote.
In any case...even when piecing the kit together yourself....it's not the price of the main components themselves that get you. It's the supporting parts, labour, shipping, dyno time, etc that end up jacking your build price through the roof.