I've been looking at some cost of living calculators and there's something that makes me a bit skeptical about them.
For example if city B is supposedly 100% more costly to live in than city A, the calculator tells you:
If you make $100,000 in city A, you must make $200,000 in city B.
If you make $200,000 in city A, you must make $400,000 in city B.
If you make $300,000 in city A, you must make $600,000 in city B.
But intuitively, it seems more appropriate to do these calculations in terms of your expenditures?
If you SPEND $100,000 in city A, you will need to SPEND $200,000 in city B.
If you SPEND $200,000 in city A, you will need to SPEND $400,000 in city B.
And this would be independent from how much you actually earn, except that you need to account for income tax.
That seems to make more intuitive sense to me, but I don't see any calculators doing the calculation like that, so is it an incorrect model? (I recognize that either way is an over-simplification)
I see there are some related questions on here but I don't think any of them address the income vs expenditure aspect directly.