Second part? Equitable? Necessary expenditures represent a far greater portion of the low income household's budget, even assuming that the high income household will be consuming luxury versions of the same items. The person with the high income can afford to save money, to invest, and many of their consumption expenditures are optional. The poor person ends up paying a far higher portion of his income in taxes than the wealthy person, on simple commodities necessary for his livelihood.
How's that equitable?