If you are not going to drive the thing, join a Supercar club! The depreciation works out about the same as membership and you have access to a wide choice of cars and can drive around 2,000 miles a year.
I admit to only doing about 5-7,000 a year in the Ferrari but that does seem enough to keep it reliable. Any less than that and it seems to have issues.
With the exception of the GTN, my lowest mileage in any Aero over a year has been 20,000 and my highest just shy of 30,000. Mechanical things that had to be done outside of normal servicing (and me bashing the cars), a set of brake discs and the rear suspension springs on the S4 which I can blame on a pot hole.
Mileage had no bearing on any of the other issues which all my Aero's suffered from and that is the water ingress, either at the roof, the doors or behind the dash.
As for the higher depreciation, yes, my 80,000 mile S4 went for £45k when the low mileage ones were selling for £53-55k. Well, 60-70,000 miles more fun for about £10,000 difference seems bloody good value to me. My flat rad which I added 20,000 miles to in around 2 years of ownership, taking it over 100,000 sold for more than my cost so can't complain about that and that includes my maintanence and improvement costs!
The GTN is an unknown quantity at the moment regarding resale. When I got it it was on 9,700 as an 11 year old car. First year of ownership added 3,000 to it which for me is feeble but have been adding lots to the Tesla and put a bit on the S5. I don't have any plans to sell it right now but imagine it's not travelling South in value.
So all in all, don't worry about mileage, enjoy the thing, if something wears out, replace it. As for 150,000 on the BMW V8's, that is disappointing if that's all. Plenty of old clunker US V8's well over 400,000 miles and still going.
