Minimum income for retirement

What is the monthly income that is needed for a couple to live on during retirement?

I discussed this question with several people above age 50 from the low income sector. We arrived at a sum of $700 a month, comprising of.

Food ($15 a day): $450
Utilities: $70
Medical: $50
Transport: $50
Telephone: $30
Miscellaneous: $50
Total: $700

A female needs a capital sum of $160,000 at age 65 to buy a life annuity that pays $700 a month. A male needs $150,000.

Most of the participants did not have this capital sum. They cannot afford to retire and will have to continue to work beyond 65 years.