The only supercharged example of the legendary British-made Vincent Black Lightning motorbike ever made, built to break the world speed record in 1950, never actually accomplished that feat. It will probably break the world record for a motorcycle sold at auction however when it goes on the block this Sunday with an estimate of $400,000 - $600,000. The one-off Vincent (above), offered at Bonhams' Classic Motorcycle Mechanics Show sale in Stafford, UK, only needs to break the current record of $520,000 (for a 1915 Cyclone) to be dubbed the world's most expensive motorcycle. Barely ever ridden, the beautiful bike is in mint condition, adding to its value. And while $600,000 seems like a lot for a motorcycle, we're pretty sure this one will only appreciate.