I hadn't noticed the price difference, but the Columbus marking simply indicates that the pistol was imported from Germany after June 2008. Subject to correction, I believe the following is a listing of the stamps and dates for P7 imports.

Arlington, VA: 1975 - 1983
Chantilly, VA: 1984 - 1988
Sterling, VA: 1988 - 2004
Trussville, AL: 2004 - June 2008
Columbus, GA: July 2008 - Present
_________________________
(1963-1967) "GO ARMY!" Nemo me impune lacessit.