I was reading Zapper Z's "So you want to be a physicist" article. I'd like to ask how much does a Ph.D Student earn on average if they are a research assistant?
Asking for an on average I would check out http://www.aip.org/statistics/trends/highlite/grad/table8.htm
It is really dependent on the school (and the source of the funding).
When I was an RA, I was on fellowship and made 18K/year (12 month support) at the beginning then 20K/year (12 month support) for the last year since the fellowship was increased.
When I did my masters (at a different school), the RAs were paid 15K/year or so (12 month support). But the cost of living there was much less.