At Christie’s latest auction in Geneva on November 11, 2013 — an A. Lange & Söhne Double-Split in stainless steel sold for 380,000 Euros. That is over half a million USD, or about 4 times the original retail price of a platinum Double-Split.
This one-of-a-kind prototype was made in 2006 as an experiment to test lighter materials (a gold or platinum case measuring 43 mm by 15.3 mm is very heavy). It apparently never went into production, hence its rarity. Apart from some obscure pieces, like this steel Double-Split, the German luxury brand exclusively uses gold or platinum for all their watches.