I've got an Oct 2004 (so facelift) C270CDi Estate. I bought it in April 05 with 6000 miles and it's now got 20000 on it.
:Touching big piece of wood now: Build quality seems fine - I havn't had anything go wrong, and it's only recently had it's first ever trip to the dealer for a service at 18000 miles. I supplied the oil and the cost was £150. They flashed the COMAND and (slighty) updated the DVD but I don't regards those as faults.
I gather that, for C Class, the Estates are still built in Germany and the saloons in South Africa.
I generally only use mine for long (200miles+) motorway trips and it does mid 40's MPG, can touch 50 if I'm careful.
No idea on prices - I think I did well buying mine from MB Direct. It was an ex-MB management car and to all intents and purposes appeared brand-new. I paid £23500 on a car that would have listed at £33500 new, so hopefully that will considerably soften the depreciation blow.
I think I would buy another, even though (bizzarely) I'd be worried that I couldn't be this lucky twice! I would like the chance to spec one from new, but the prices (especially with the 'must have' options) just look absurd.