If that's all you care about, paying $400 like I do is silly - you can get it much cheaper.
The $400 phone I get takes fairly good photos (it's one of my main criteria in deciding on phones). Sure, if I want great photos, I'll have to pay more. I've decided that an extra $1100 over 3 years is not worth it for the marginal improvements in photo quality. But I know for some people it is, and that's fine.
Regarding the boots, we're both saying the same thing, which I think is not what the author is saying: You're fixing a time interval (e.g. 30 years), and calculating that it's cheaper to get the expensive boots vs the cumulative cost of cheap shoes in that time period.
When you fix the time interval (e.g. 30 years), comparing rates vs comparing absolute totals is equivalent.[3] What I typically see is that people take this equivalence and begin to compare against different time intervals (option X is for 2 years, option Y is for 5 years). This is what leads to so many silly blog posts saying you'll never get a better investment than your employer's ESPP benefit, because you get a huge return.[1][2]
In any case, the author isn't using the Boots Theory. He's looking at cost per use - and not utility/cost as a whole.
[1] https://thefinancebuff.com/employee-stock-purchase-plan-espp...
[2] I'm pro ESPP - but looking at those claimed return numbers is almost useless. It's trivial to make more money with, say, a mere 5% annualized return.
[3] When comparing investments, you also need the same input. It starts getting messy - which is why the standard advice is to convert to absolute dollars and compare.