There's a great book called "Your Money Ratios", which I really like for boiling things down to straight forward, manageable, rules of thumb. True, it's far from full on Mustachian, but if everyone followed "Your Money Ratios", we'd be in a lot better shape. Anyway, I know he recommends a 1:1 ratio for loans:starting salary for undergrad. I believe he then says no more than 2:1 for grad school. That part I'm a little fuzzy on.
From my experience, I can say that my $30k in student loans would be manageable on my salary of $35k, but can't imagine having too much more than that. I think my salary is a reasonable estimate for most average undergrads, that is to say, not STEM, accounting, etc. But, I think you also need to take into account the need for further education. If you know starting undergrad that you will have to go to grad school to get a job in your field, it is just craziness to start out with $40k, $50k, etc. in loans. On the other hand, if you are going to school to be an accountant, maybe you can afford to take out a bit more.
Of course, we all know that we need to minimize the loans as much as possible across the board; it's really hard to imagine a scenario where you would truly need to take on more than $30k or so in loans to get a degree. If you're paying full freight to go to an in-state public school, you can switch to part time & pay more as you go. If you're on some form of scholarships or grants that require full time status, then that should mitigate the costs enough that you still wouldn't need to take out an outrageous amount.