Most PhDs in technical fields get paid tuition and a stipend.

On the order of $15-20K/year. It's hard to save money when you've got a poverty-level stipend.

His comment implied that grad school is like undergrad where you accumulate lots of debt.

60K debt in student loans from undergrad is a world of difference from "wish I could save more".

My comment implied that there are people who are broke from grad school.

Last time I checked my bank account, that's still true.

The many grad students I've known aren't close to rich -- but aren't broke because of school at all.

Most earn ~6 figures when they graduate, unless they go into academia where income growth is slower but benefits are better.