The release of the NL tanked the resell market for everything else. Fair price for SLCs is under $1500, and ELs can be had for pretty near that price as well. Watch FB marketplace, KSL classifieds, and the RS optics classifieds. Don't be afraid to make offers.
For Leica, I'd stick to Noctovids, but they're rare on the used market. Stick to Victory SF for Zeiss.