In this auction, a red Hella KL 6 was sold. However not a Eisemann.
The other Hella KL 6 from the seller was sold for about 250 €.
I suspect that the red dome is rare and hard to find. Regardless of whether Eisemann or Hella.
http://www.ebay.de/itm/HELLA-KL-RUND...53.m1438.l2649