You might, theoretically, spend a few £k if you had to do all the big jobs - radiator, clutch, suspension bushes, oil cooler, cam belt etc - all at once. But in reality those are ticked off over the first 5,6,7 years of the car's life as I have done ( correction, still on original clutch) but then they are sorted for the next 5-10 years or life (powerflex bushes for example). Allowing £1k could be realistic but get a well-maintained one that has had all the biggies done fairly recently, as most have now done, and there is every chance you might have nothing more than servicing costs.
I used to be on the now defunct GTVV6.com & several members graduated to Massers. They all loved them but either quickly sold them before getting a big hit or lived with ordinary running costs of £3-4k pa with the daily possibility of something much much more cropping up. Oh, & they rust quite badly too, much worse than GTVs - that was another reason for selling them on. Also these were mostly guys who had bought 3.0 GTVs new for up to £32k, rather a different cost expectation/disposable income level I would assume to people buying them now for £3-6k.
So the Masser is a phenomenal amount of car for the money but expect running costs to be in the same league as other £50k-£150k exotica (even though, or because(?) it has so many components in common with Alfas).