here is the link that suggests the concept:
http://www.bravenewlife.com/01/changing-perspective-income-thinking-vs-expense-thinking/
it is wrong because it divorces two things when you should be combining them. here is how it should work…
income – expenses = throughput. in his case, he makes $50,000 a year, or as i would figure $33,800/year after taxes in actual income that he can spend.
that is $92/day (divided across 365 days in a year)
apparently the expenses for his family are $80/day.
in the situation where it costs $200 to hire a plumber, it is not 4 hours of his time as income thinking would suggest.
further it is not 2.5 days as expense thinking would suggest.
his daily throughput is 92-80, which means that he makes $12/day… so a cost of $200 is really 16 days or half a month.