I think that developed nations have a cost of living index, which may be used to determine a poverty line and a minimum wage rate that allows workers stay above the poverty line, ideally, significantly above the threat of poverty. Which is probably only achievable through unity. Individuals don't have bargaining power unless their particular skill is in high demand.
The CPI is a ratio expressing the change in cost of various goods. It is good for measuring trends of cost over time. I am not sure how this can be used to find values of the actual cost of living, rather than relative ratios of cost of living between regions. but there is an interesting bit to this... the relative weight of various consumer goods in the calculation of CPI. It is as follows:
Housing: 41.4%
Food and Beverage: 17.4%
Transport: 17.0%
Medical Care: 6.9%
Apparel: 6.0%
Entertainment: 4.4%
Other: 6.9%
So, this lays out what economists believe the distribution of household expenses "should" be. This is helpful, in that it can provide a method for calculation. But we first need to understand what a "minimal" rent or mortgage would be, or what a "minimal" amount of healthcare is... etc..