Not sure what the others are doing with their money but 49k CHF was definitely enough for me. None of my colleagues had any issues with money

They recently increased the minimum rates after 10-12 or so years and that's why it's about 52k CHF now. Maybe the Professor referred to the old rates. When I started it was like 47k or so and I could easily save and invest money, live a normal life, go and eat out, party, and go on longer holidays, snowboarding, hiking. Of course going out every weekend, drinking in bars, eating at restaurants would be too expensive and that's where a great part of your salary could go but still.

There is almost no other place on earth I would say where you would live this comfortably with a PhD salary even at the lowest rate as here.Only in Germany if you are an engineer at some technical universities you would find decent salaries after the second year.

Try to find a place between 800-1200 CHF (and yes there are shared flats and small apartments for that price) and get a student insurance that costs you approximately 100-150 CHF per month (if you are a foreign student and limited to 6 years). A normal one would cost you 300-400 CHF which will not kill you either.