You might be pushing it a little with an older edition, you always want to have access to the lastest info. The Washington Manual is now on the 31st edition. Have you ever tried shopping at Amazon.com Marketplace? I have bought a ton of great medical texts there for great prices...I bought the new ed. Wash. Manual for $28. Yes, they are used, but you can read the seller's descriptions and decide for yourself. Good luck!
Monika 🙂