I own one coat. It is dark green, waxed cotton, and cost roughly four times what I had ever previously spent on outerwear. I have had it for six years. It has been reproofed twice, had a pocket restitched once, and been rained on in four countries.
The maths people do
The usual argument is cost-per-wear: an expensive thing worn a thousand times is cheaper than a cheap thing worn twenty. This is true and it is also not why I did it. I did not do a calculation. I bought it because I was tired of thinking about coats.
That is the real return. Not money — attention. A decision made once and then never again is worth more to me than the sixty dollars I may or may not have saved.
Where the argument breaks
“Buy one good thing” is advice that requires having the money for one good thing at the moment you need it. If you need a coat in November and you have thirty dollars, you buy the thirty-dollar coat, and you will buy another one next November, and this is not a failure of character. It is what being short of money does: it makes everything more expensive over time.
I could buy the coat because I had a windfall that year. The advice is fine. The framing — that it reflects some superior discipline — is not.
The practical bit
If you do buy one, buy it from someone who will repair it, and find out what reproofing costs before you commit. A waxed coat that is never rewaxed is just a heavy coat that lets water in. Mine takes an afternoon and a tin, once every two years.