I had a 5-speed 400I, bought it for 27K sold it for 25K and put over 25K into it over 7 years to drive it for about 22,000 miles.
I did all the work myself, as mentioned earlier parts and frequency of maintence are the issue. The engine on the 400 uses one long chain to drive all 4 cams, has really short valve guides. The water pump/oil pump unit is chain driving off the crank, so to remove it the engine comes out, the oil pan comes off and the front main bearing needs to be removed to reseal the water pump.
Ferrari recommends removing the engine and "servicing" ( which includes a valve job) it every 40,000 miles. I went 52K and when I did remove and disassemble the engine, I found the valve guides so bad I could drop a valve, the timing chain was wearing a grove in the housing, engine was beyond safe. Ferrari was right every 40,000 miles!
