"Patent drilling" ReichMark 335, "Trumpf" 360 ReichMark, "Tugend B" began at 245 RM with an popup sight for 15 RM,
Montage eines Zeiss-Zielfernrohres "Zielvier"(4x) - 170 RM
Montage eines "Anker" - Zielfernrohres, drei oder vierfache Vergrößerung - 95 RM
May have been other scope mounting systems or other scopes may fit the same.
Neptun started at 495 ReichsMark and may have topped out at say 700 RM. These values probably apply to the late 1920s and 1930s. I am curious what date range you are considering. I believe the values penciled in a catalogue I have are in U.S. of A.:
Neptun - 155.00
Kind Regards,
Raimey
rse