I think BMW is more expensive than Audi. BMW is more reliable and has a lesser cost of maintenance than Audi. Both are luxury car brands. BMW is owned by BMW AG. Roll Royce is the most expensive brand of BMW.
Audi is owned by Volkswagen, the same brand that owns Buggati, Bentley, Lamborghini, Skoda, MAN Trucks, Scania and Porsche.