This post made me happily spend ~$100.

Quick tip for anyone trying to get older editions of some of these books: use Abebooks

For example, some of the drawing on the right reviews mention that the 1989 edition is better. I find this happens with many new editions of older books.

You can find near good as new editions of older books on Abebooks, at very reasonable prices. I used it to get a great copy of SICP, and just now ordered a version of How To Win Friends And Influence People published during Dale Carnegie's life, as Paul Graham recommended.