I found that
some Ph.D. programs pay monthly salaries like real jobs (EUR2300/month for a period of 36 months): Medical University of Vienna, AT
many pay minuscule monthly stipends like pocket money (PLN2600/month for the first two years, and PLN3600/month for the next two years): Jagellonian University, PL
Why is this difference? And, how can I distinguish between these Ph.D. programs?
In the second university, why should someone spend four years of his life surviving only on pocket money when they can earn more by enrolling in the first program? I.e., if the above programs want to attract students, why would someone apply for the second one? I mean, what would be their motivation?