MCD Racing produces radio-controlled racing cars, 1/5 the size of real vehicles. These are not toys - they are highly sophisticated machines capable of winning world championships. These cars are capable of world record speeds of an unbelievable 260Kph (161mph)! Obviously they must be very carefully designed, perhaps with 1/5 the effort that goes into Formula One full size equipment.
The 1,000+ parts involved in such vehicles are typically produced using injection molding at a cost of USD$20-40K, with a month of turnaround time. However, MCD invested in a Dimension 3D printer and has used it to develop over 200 prototypes at far lower cost and much faster turnaround time (days).
But note - the parts produced on the 3D printer are not actually used in the final vehicles. While parts are pretty strong, they simply won't withstand the extreme environment at ultra-high speeds. Instead, the 3D printed parts are used in lower-speed testing to validate their function before full-on aluminum injection molding is attempted.