Used car prices

Scanning the used car mail box stuffer today, just to see what's what.  We have one year old Cadillac CTS (the four passenger Beemer wannabe) for $30K.  Whereas we have bunch of pickup trucks going for more.   Used to be a Caddy was worth twice as much as a pickup truck.  Not anymore.  For real value, try a Chevy Suburban for $47K.  Plain four door drive-to-work and go-to-the-store  sedans, Toyota, Chevy, Kia, and Ford run in the $16-$20 K range.  Used. 
   I wonder what will be available when my Mercury Grand Marquis wears out and needs replacement?