Thank you all for the ongoing comments and info. I'm in a bit of a holding pattern while I keep an eye on ebay and cars.com (any other suggestions to keep an eye out?); as I believe others have suspected and commented, it seems like the prices for a Roadster are starting to come down a bit (or so it seems to me).
The earlier tip about ideal miles on a standard charge - I'm keeping an eye out for that as an indicator of battery status. And mostly focusing on getting other things done (who installs a solar system in the winter in Oregon??), so that when the right car does show up, I'm ready to move.
I'm also keeping in touch with the CPO folks, but I'm thinking that to hit my target of <$10k net to drive the Roadster between now and Model X, I'll have to go private on the front end or the back end (hopefully not both).