Tom, you've pretty much captured the essence of it. It comes down to what the builder values and knows (some inexperienced folks don't know what they don't know and end up making decisions they learn to regret, but that's learning). Without getting too wonky about economics, money is just an IOU for value exchanged from one person to another. For some the best use of their value production is scrounging stuff, spending time rummaging through wrecking yards, dumps, barns, whatever. For others it might be inventing a new design of trailer that meets a market need and lots of folks exchange money for the trailer. If you're better at making the trailers for others, then you employ the value you earn that way. If you're better/more willing at rooting through the discards of others then you employ that value. Some folks are very creative and skillful at fabrication, others need the help of those kind of folk. Different roads to similar destinations.