I think John is not far off the mark with his guesstimate if you maintain your pride and joy to a high standard and pay for proper peeps to do the work for you.
Rodman 870 with twin engines costs for me are approximately as follows:
Haul out jet wash block of then relaunch £380 (MDL Cobbs Quay), Anti foul paints 5 litres for 2 coats £160 (Seajet 033), Anodes including 4 no 100mm round on stern 2 prop anodes and 2 shaft anodes around £120. Servicing of 2 engines £1200ish but this includes gearboxes + checking shaft and earth bonding continuity checks. I then choose to pay some to wash polish the exterior and clean stainless work which usually works out around £450 however this year I am having a few fiberglass dinks sorted and the cutting and polishing done hopefully extra special by a couple of Sunseeker valets + they are renewing the plimsoll lines which have become annoyingly damaged and redoing all sealants so will cost considerably more. I am also having the fly bridge cover replaced as mine got damaged during the last storm we had that's another £460
Last year I had 2 new batteries plus and some pump or other replaced another £550
I will do all the internal cleaning and polishing myself (cause its warmer in the cabin). I have been promising the boat I would have a go at cleaning the bilges for 2 years so may well do that, they are not bad but I just like the boat to look nice.