The 1970 Plymouth Hemi ‘Cuda convertible is the rarest and most valuable muscle car most enthusiasts will never see in person — only 14 were ever built. Back in period, buyers largely ignored it, put off by insurance costs and a price tag that made little sense for a mid-size car. Decades later, that same scarcity has pushed individual examples toward eight-figure sales. Read on to find out how a commercial failure became the most expensive muscle car in the world.