Well, the value of a mainstream Italian car is rather buttery, in that it melts rather quickly as soon as you take it outside.
Thing is, it's all about perceptions I reckon. Traditionally Italian cars are meant to be poorly built, unreliable, rust quickly, be a butter to start on winters' mornings. But from what I have heard of the newer Alfas, they are very well built and reliable. People still have the old perceptions of them, so they are harder to shift hence the faster depreciation.
From what I have heard, recent Mercedes are rather poorly built. Even Jezza, who is a big fan of AMG cars, made several remarks about it in the last series of Top Gear. Yet they still retain their value because everyone thinks "Hey, Mercedes! Shall I buy a 100,000 mile example or should I get one that has been fully run in?"
Thing is, the dealers have cottoned on to this so the prices on used 156 GTAs bear no resemblance to the Parker's price guide! That reckons a tad under £15K for a 1-year old, 10K mile example, fully prepared from the dealer. I haven't been able to find one of that age under £19K. Wait a tick, just checked the information on Parkers and that is referring to "target sale price", not "sticker price". Could come in handy for haggling! Plus I think those £19K cars might have extras.
Wait until you have got a house with a garage, Adam. Just wait!