This was DC Comics late and short-lived attempt to do what Marvel had done so successfully throughout the 1960s and reprint classic Silver Age material or at least make available their material to the likes of Wham, Smash and Pow comics. But Super DC didn't last. High grade copies of all issues are tough to find.
#1 had free gifts of a Batman poster, a Wristwatch Calendar and a Superman Magic Disc, all in a manilla envelope. Quite difficult to find all this intact and adds £40-£50 to the values.
Note: some PR issues may have no value. Selected issues in FN, VF or VF/NM may not exist in some titles.