Which is cheaper - new or 3-year old over 8 years?

I guess I'm indirectly asking the difference in maintenance cost between a new model and a 3-year old model if kept for 8 years or longer. At what point, does DP start accumulate significant repair cost?

As a comparison, if I intend to own a car for 8 years or longer, I would just buy it new, rather than getting a 3-year old used model. Not sure how it compares vs Class A DP...