Whenever you look at an Audi, chances are you’ll also be looking at cars from its big rivals, BMW and Mercedes-Benz. In the case of the A5 Cabriolet, we’re comparing with the BMW 4 Series Convertible and the Merc C-Class Convertible. A left-field alternative could also be Ford’s Mustang convertible. All four are similar when it comes to purchase price. While the exact running costs will vary depend on which models you go for, we’d expect the extra power you get in the Ford to be counteracted by the high fuel costs and surprisingly high repair and maintenance costs, making it pricier to run than the rest. But for the German trio, there’s very little to separate them, which means that in your quest for premium top-down motoring, you’re probably better going with your heart than searching for the most cost efficient option.