After a frustrating search (googling "used Pimsleur Russian" brings up mostly reports/reviews of having used the Pimsleur method) I finally found a site that sells used Pimsleur cds (Russian I Comprehensive for $129) and then buys them back for $100 as long as they're still in good shape. If they don't have in stock the exact title you need next, you can 'reserve' the next copy they get in, and they can from experience estimate the likely length your wait will be. Sorry if this has been discussed before -- I tried searching here on 'used Pimsleur' and had the same problem.
Here's the site: Used Pimsleur
Val