I moved last year and got rid of a lot of stuff; to my surprise, not only do I not miss the things I got rid of, I find myself wishing I'd kept less.
The trouble comes when optimizing for enjoyment today causes pain tomorrow.
I'm pretty much there. And having got there, I'm not convinced (yet) that it's the right goal at all. Hard to divest from it, however, since enjoyment is hard to walk away from.
Accounting for depreciation, interest, insurance, actual service bills and petrol, I ended up with A$0.25 per km and A$4150 per annum, so ATO-sanctioned business travel compensation always rightfully seemed to be a handout to me.
A new BMW can easily cost 6x as much, hence "average body temperature".
An oldish paid-off relatively inexpensive car will absolutely do better than that on average. But it's actually not unreasonable that the business deduction bases costs on something like a late model leased midrange sedan like a sales rep might use to drive clients around.
I think there's another take on this advice, that it's not about optimizing spending, but simplifying your life and obligations by avoiding the burden of ownership and minimizing debt.
Of course the rational break-even level math for some of these purchases can be analyzed, including taking into account tail risks and hassle costs.
But I think the point the author is missing is that some things are affordable luxuries that people enjoy. For a long time I didn't have a car in the downtown part of a city I live in. Public transit+rideshare+zipcar was a totally fine substitute (like the author).
But owning a car is better/easier/more enjoyable/more freeing! We didn't do a fine-grained analysis on how much using zipcar+hertz would cost vs buying a car. The car isn't costing a significant percent of our income, we were annoyed with alternative and wanted it, so we bought it.
If you used a blender 2x a year and it cost $1 to rent vs $30 to buy, would you really consider going through the hassle of saving money to deal with renting a blender? I'm not suggesting a car is the same significance for all, but certainly it can be rational to own one even for people in the same position as the author.