Bernie Ecclestone, effectively the owner of Formula 1 and a very, very rich man, made a tidy profit yesterday on a used car.
   
A used Mercedes-Benz, to be specific: a 540K Special Roadster.  It was sold at the RM Auction in London for $8.1 million.
   
Ecclestone is trimming his collection, selling several other cars, and is expected to reap a total of about $30 million by the time the auction is done.
   
But he could do better. After 15 minutes of bidding, the 540K went for more than twice the pre-auction estimate.  In fact, the car came close to a record.  The top price paid for a car is about $11.8 million in 1987 for a Type 41 Bugatti Royale.