20 - 25k for a good one.

Big ticket items are:
Vanos
Road bearings
Chains and guides
Full suspension refresh including shocks and springs
Clutch and flywheel, 60-80k miles depending on driving style, the clutch is small at 240mm, the car has a lot of torque, so they're not easy on them
The brakes, they suck, there is no escaping that, stock disks and pads are only ok, you need to be very careful not to cook them, ideally, a decent BBK.
Interior refurb, most of the interiors are nappa leather.
Wheels will need a refurb, lepsons in the UK are the only ones who can get it right.
Full glass out respray, every single one of them has body issues and you'll find that you'll be at 80% of a full respray so just do it.
Headlights suffer from adjuster failure, after late 02 you can't split them so the car will need new lamps.
On top of that, shove 2k on the list for bits that you'll find that need to be replaced.