Stating only the $200.00 difference is rather meaningless. What is the dealer price for a new one? A couple of keystrokes and you have more than a few choices for new and rebuilt.
www.fastlane.com (The sight you made the post to)
www.mbpumps.com
www.benzbin.com
www.bestforeignparts
and no doubt many more, including re-cyclers Potomac.
mbpartsonline.com

Looks to me that mbpumps is the winner on price for a re-built pump.
$140.00 core $130.00.

Fastlane is almost $400.00 for a rebuilt.

Steve