The V8 3.5 Cabriolet is repeatedly described as rare (roughly 1232 built) and as the final year of hand-built two-door production, and it consistently clears $300k with sales reaching $346k, $357k, $380k and higher. Commenters maintain a running tally of the cars that have crossed the $300k threshold on BaT.
280SE 3.5 Cabriolet as the market pinnacle
Mercedes-Benz W111 Coupe / Cabriolet · market