A Ferrari has no particulate filter to block and no EGR circuit to soot up. What it has is heat, and an owner who — very sensibly — does not drive it every day.
On direct-injection models such as the California and 458, fuel goes straight into the cylinder, so it never washes the back of the intake valves. Oil vapour from the breather bakes onto them instead, and turbo or high-compression heat sets that deposit hard. The F430 and 599 spray fuel onto the valves, so they rarely need that work. Add long periods parked between drives, and short warm-up runs when the car does come out, and deposits accumulate on an engine with very few kilometres on it.
We work on these carefully, we quote after we have looked, and we tell you what we find before anything is touched.