DWDM Optics cheaper than CWDM Optics?

Hello, fs.com offers DWDM optics that are cheaper than CWDM optics: CWDM 80km 10G for 600$ http://www.fs.com/c/cisco-cwdm-sfp-plus-2425?70-80km DWDM 80km 10G for 420$ http://www.fs.com/c/cisco-dwdm-sfp-plus-2485?70-80km This is significant. Is this for real? Has anybody bought their DWDM optics? Going with DWDM and passive Mux/Demux seems to be cheaper nowadays than going with CWDM. Regards Karl