The overall idea is better expressed as – value stuff based on how important it is to you vs just the dollar amount associated with it, which is pretty generic and obvious advice. Trying to simplify it down to "cost per use" or some other similar metric is pointless. Is the $3000 flight ticket that you use once worth more or less than a $1000 phone you use thousands of times or a $5 coffee you drink in one gulp? No one other than you can answer this for yourself.
of course it's not possible to come up with an ironclad set of rules on how best to spend money, especially not in the space of a single blog post. but that doesn't mean it isn't worth trying. if nothing else, it helps to become more intentional about how you spend your money, which most people would probably benefit from.
I personally don't find the concept described in this blog post very useful. I prefer to think in terms of annualized/amortized costs, especially within the perspective of money-stress-time tradeoffs. I could see others finding it helpful though.
