did a quick ebay search. 991 turbos and the 720s are following similar depreciation curves. makes sense as neither is limited. The mclaren however, like most exotics, is very mileage sensitive. Non-GT 911s in general are not as mileage sensitive.
2018 720s - msrp 300k - selling for 230k and has 6500 miles. (25% depreciation / 70k loss / 2 years)
https://www.ebay.com/itm/2018-Porsch...MAAOSwFqZeY7sM
2019 720s - msrp 350k - selling for 260k and has 6000 miles (25% depreciation / 90k loss / 1 year)
https://www.ebay.com/itm/2019-McLare...wAAOSwfEJeVO~e
2018 991 turbo - msrp 220k - selling for 170k and has 13000 miles. (23% / 50k / 2 years)
https://www.ebay.com/itm/2018-McLare...8AAOSw4PBeR8pR
you are paying for the exotic experience, doors going up, engine on display behind your head, and paparazzi treatment when you get a 720s. Because pretty much every lay person will ignore a 911 when a mclaren/lambo/ferrari is around. This can be a good and bad thing.
Personally i'm over it.