I guess the reason why I used the car analogy, was that to me (at least from a recreational diver's standpoint), is able to dive safely without the need for large investment, and the picking up groceries example was what I had in mind. I'm sure the high end reg and a M3 would be more enjoyable regardless of what type of diving/driving, but so would the maintenance cost (if not DIY). And the main point of the thread, is to see if that overall long term ownership cost would justify it, vs just buying a new one (and forget about the hassle/cost of getting it serviced). A high end reg would probably give you 10 - 20% easier breathing under deep/cold water, but above 80 feet, I don't think the difference would be noticeable, if any (correct me if I'm wrong since I've only heard this from others, as I don't own a high end one). And for those of us who live in a small apartment with limited space, DIY might not work since we don't have space to store a tank.
I think the car analogy can be applied to regs perfectly. There are people who loves driving sporty cars like M3 whether to work (diving for work), racing (technical diving) or groceries (recreational diving). And there are people who likes to have a low maintenance, reliable car from point A to point B just for weekend groceries. Over half of the experienced recreational divers whom I've met on dive trips still use rentals. They still enjoy diving as much as those who has their own gears. Then there are those like
@Bob DBF who likes to drive his '68 Mustang (vintage regs) for any activities.