The problem is that in real life, most such cases (of buying the more expensive item) don't result in a pure savings, but rather, leave you better off in some ways and worse off in others. The cheaper shoes, IOW, will not actually be so bad that you have to replace them entirely, and you will in fact end up with with more liquid savings. The temporary discomfort and greater savings are much harder to compare to the alternative than the example suggests, so wealthier people do not always have some obvious choice that leaves them better off in every way.
So, on top of that, it's not an issue that is fixable simply by pointing this out to the poorer person and loaning them the money.
But I'd have to concede that you'd be right to say it still doesn't fit the boots analogy with out some rather lax semantics around up front vs long term cost. You could also argue that any individual might get lucky/unlucky and so it's not clear cut there, but I think it would be fair to argue that in aggregate the outcome on cost is a reasonable example.
