This Orshansky person used estimates and approximations to come up with a rough "this is what it takes to not starve" number, in the absence of sufficient high-quality data to calculate something more precisely.
If you trust inflation / cost of living numbers, they're a measure of how expensive life is overall.
This is the correct way to do things. The methodology of the original SWAG is not relevant to how to update it over time.
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If you take apart the original estimate into all the different things that made up household expenses, and adjust those separately for price changes and substitutions and such, and our or back together... you're just putting in a ton of extra effort to re-build the "adjust for inflation" calculation from scratch. With tons of room to make mistakes, as demonstrated in the article.