Last new car I bought was a '91 Capri when I sold my MGB because I needed a backseat with seatbellts for my little kids. Since then, I've only bought used cars. For a while, while funds were used for things other than cars, i'd buy Cadillacs for $6K drive them 3 or so years and sell them for $3K. Talk about cheap, luxury transportation! Then I gradually moved up the ladder to my more recent purchace of a 2006 SL500 in 2012 with 28K miles, practically brand new from CarMax for $38K. That's almost a 100K sticker car for a 60% discount that was barely broken in. And, I was able to purchase a 6 year, 100k mile warranty from CarMax. I love the car. My most recent purchase is a 65K mile Audi A6, 2003, for $5K. With 4WD and heated seats, it's perfect for winter.
IMO, the sweet spot for pre-owned is three to four years old, 25-45K miles. CarMax has quite an operation in this market, I and others have been very pleased with. Friend just bought a 2011 BMW 550XI there with ALL the bells and whistles, 35K miles, in spectacular shape for $42K. What was that new? 70K+? Let someone else eat the steep slope of depreciation.