Did stone age people have an income of slightly below [USD]2 a day?
No. "Income" is an anachronistic way to deal with hunter-gatherer or settled resource extraction or early agricultural people. Income is concept that relates to accounted earnings, which develop in antiquity and medieval times, but most strongly in early modernity with the birth of capitalism as a social relation. As "income" as a concept or as a social relation didn't exist, people did not earn incomes.
Ten thousand years ago, there were only about six million people on earth. On average they lived about thirty years and supported themselves on the equivalent of less than two modern American dollars per day.
10000BP appears to be meso-lithic, and Galor O, Moav O 2007, The neolithic revolution and contemporary variations in life expectancy, Working Paper, Brown University, Department of Economics 2007-14 http://hdl.handle.net/10419/80105 indicates that the lifespan was around 30, including infant mortality.
The crux of the question is: was meso-lithic life equivalent to less than USD2 per day? In particular, the concept of an equivalence between USD2 in 2014 in the United States where wage labour in advanced industrial capitalism is the way of life, and the way of life of pre-agricultural meso-lithic humans.
From the material relating to the attempt to form a long run wage price series in England, and from the general work regarding long run attempts to explain "inflation" and acceptable standards of living (cf: Measuringworth.com 's paper-sets): it is unreasonable to equate standards of living in the meso-lithic with a monetary income in an advanced industrial wage labour society.
The history of ways of living, and the social organisation of ways of living (including waged labour, and purchase of social necessities on an open market), strongly favour not making broad comparisons across time in terms of different ways of organising society. The anachronisms involved become counter-productive in the extreme, and hide the actual ways in which people live. Even in very short stretches of time, between 1800 and 1850, subsistence and how people experienced activity vary considerably such that ideas as to whether "work" is onerous in capitalism is a difficult question (EP Thompson 1967, Time, Work-Discipline, and Industrial Capitalism, widely reprinted but first in Past & Present).
USD2 in 2014 has no meaning in terms of how meso-lithic humans sustained themselves. Meso-lithic humans lacked wage labour, a cash economy, commodities for purchase. They did not support themselves on the equivalent of less than USD2 a day; as how they supported themselves has no comparable value to the methods of support that USD2 entails. The quote is a sloppy metaphor that produces more confusion than clarity.