I intend to cheat.

But seriously, I think I'll be quoting the actual prices I paid for the parts I'm using, and throw myself on the mercy of the court. I'll be using some stuff that arguably has little or no resale value. Stuff like used shifter cables that came off other projects and was able to shorten and reuse for this one. I've got a set of nice used tires; have no idea what used tires are worth, but they were purchased at a yard sale in a box with a nice basket, two bells a rear touring rack and some clamp-on aero-bars for a grand total of $20. What's a slightly-pitted, no-name crank spindle worth, at bike swap? A buck? Who would want it, when there's another guy one table over who's got a box full of near-perfect ones for $5 each? That Redline frame, on the other hand, sure it looks like a zero-value item, coming out the dumpster covered in dead leaves and moss, but it's straight, and the rust (even in the BB) is actually not too bad. Now that I've got it stripped and cleaned, that Tange MTB Cr-Mo sticker on it and its fairly light weight might fetch $20 from a person who's always wanted to have a triple triangle frame.

Fudge factor, I guess.