The margins on used cars are many times those of new cars. Most dealerships do make more money from their used cars unless they are very high volume.
Most used car models are based on retailing a high percentage of dealer trades as they are the highest margin source of inbound vehicles.
Easy source checks are any research on CarMax, a light review of any of Pollacks books(Velocity, Velocity 2.0, Velocity Overdrive)
Source: I am also a domain expert in the auto industry.
No, they're not. New car trades are liquidated at auction houses.
Source: I work in the automotive industry.