This, and how much you're inputting and outputting in terms of cost.
Also, the benefit is that you're driving something newer with lower mileage. I am in no way scared of 200,000km. Only scared about it affecting the money I get out of my car used to put into something better.
Ja sorry I edited my post above to add more stuff to it.
It's a fine line and the benefits are about a lot more than just money. As you say comfort and other things.
You know if you had to trade up from a car without heated seats to one with heated seats for instance and it was also slightly lighter on fuel then the comfort + economy benefit would negate the minor difference in cost.
If and only if you started second hand in the first place and cut the depreciation out.
If you had to cover that from brand new you would be pissing money away.