In July last year i bought my 156 2.5 for £2500 and i love it. Over the year it has cost me £15O for its 96k service and £246 for a new rad. I think that is quite reasonable. The previous service history i have for the car adds up to £4813 over 7.5 years for its previous owner which dosent seem bad but i guess you would have to calculate approx £20000 of depreciation on top of this. This works out to approx £3300 a year , still not bad i dont think.
speaking as an ex main dealer. All new cars have VAT on them so you can take 17.5% off the new price as soon as you drive away from the dealership. so your £20k alfa is suddenly a £17k alfa. then take the depreciation as a second owner car and hey presto £5k lost in a day! Thats why you are better buying a 12 month old motor than a new one.