You basically pay for the depreciation of a car..for example say we have Car A that costs $50,000 and will cost $35,000 in three years, a decrease of $15,000. Then say you want to lease it for the duration of the three years, you'd simply end up paying $15,000 over the three years in monthly payments.
Now also say there's another car that costs $30,000 to begin with, and after three years it's depreciated in half to $15,000. You'd still end up paying $15,000 over the three years for this car.
So in the end, you'll end up with much more "car" for the money. And plus with a slower depreciating car you'd of course end up with a better more valuable car.