The problem with Audis is that resale values are based on them having optional extras. The people who calculate these percentages base them on list price and average historical sale price with several extras, but take no account of additional extras. Thus a car that originally cost list of £35,000 + £15,000 for extras may be given a residual of 40% after three years, but that's 40% of £35k, not £50k, making the car worth no more than one with the standard extras. Glass's prices for late model A6 2.0TDIs include metallic paint and DVD satnav.