You have a point the Harry Smith is 60$. I haven't listened to much of it, just some songs I copied from a friend but one of these days soon I must get the whole thing. Have you tried anything from the Yazoo lable? It's mostly delta and piedmont style blues but some very good choices of cuts on the compilations. Some of those instruments these guys played were of their own invention. Robert Johnson started with a length of bailing wire nailed to a broom handle with a cigar box on the body.