I don't think you're getting it but let's try a different tack.
We're not talking about like with like, we are talking about the longevity of an expensive car versus a cheaper car.
So mini sell as many cars in the uk as Fiat do (give or take a couple of thousand)
Go look at the autotrader figures for cars that are 10 years old and above, there are double the amount of minis still up for sale than there are fiats (944 Fiat's, 1,943 minis)
Volvo which sells 20,000 less cars a year than Fiat do, at 10 years, still has 1,297 cars on autotrader (350 more than Fiat after 10 years)
I can compare Ford if you really want, Ford sell 5.2 times as many cars a year in the uk than Fiat do (which is why I'm confused you're arguing that Mercedes is not like for like because Mercedes sell more, then want to compare Ford)
In any case after 10 years and bearing in mind that fords are a little more expensive than Fiat, after 10 years there are still 6,931 fords up for sale, which equates to 7.3 times as many Ford for sale compared to Fiat, so fords continue in greater numbers after 10 years than Fiat, a higher percentage of fords are still in circulation.
I'm not going to keep explaining every brand but if you go and look you will find that there are less cheaper brand cars around after 10 years than there are expensive cars, the actual number of cars any one manufacturer sells is irrelevant as you can still the same trends if you factor this out. Like it or not, Fiat are a cheaper brand.