This depends heavily on the country. In Denmark a PhD student in any discipline will earn a salary of about €2000/month after taxes. However the positions are s

This depends heavily on the country. In Denmark a PhD student in any discipline will earn a salary of about €2000/month after taxes. However the positions are somewhat more competitive as a result: professors have fewer PhD students at a time than American professors do, usually only one or two, sometimes three. The downside of that is that it's harder to get into grad school. But the upside is that the situation of lower ratios of PhD students to existing professors makes getting academic jobs after graduation easier, because the number of new PhDs graduating is not hugely out of proportion to the number of academic positions opening up.