I remember checking how leasing a Porsche for 3 years would cost me less than half of the value the car would lose in that time.
In general, though, the best way to combat the depreciation of a car's value is to take out a long-term 0% interest loan, provided of course that you can get it. This works because (1) inflation reduces your effective net expenditure on the car; (2) you can take the cash you would have spent on the car and invest it instead; if you even conservatively get 3% returns a year, you've still come out far ahead.
Regarding (2), if you can't afford the car in cash, then you can't afford the car. That's always been my motto. Financing is a choice; it should never be something you are forced to do, unless this is your first car straight out of school and you just have no money yet.
The car retains the majority of its value, they enjoy the car, they're not actually spending massive amounts of money like you seem to think they are. It's essentially a hobby item that they enjoy driving.
And it's only a proportion of my friends, some just get other cars that are a lot cheaper to run.