Either you have parents who can help, then it doesn't really matter whether we are talking about 5k, 25k or 50k (from a structural perspective), or you don't. If you don't have anybody who can help, it doesn't matter whether you cannot come up with 5k, 25k or 50k.
One of the reasons German students protested 600€ a term (1200€ a year) fees was that it furthered the divide between people who could afford university and those who needed loans or other money. If you could already afford it either way, 1200€ didn't make much of a difference either. If you already struggled massively to keep yourself afloat before that, coming up with 1200€ more was sometimes quite impossible.
If you cannot take out a loan (any form of loan), then you are screwed unless you are already privileged enough to study. If you are, 5k, 15k or 50k make little actual difference.
There are, in my opinion, two possible ways: no fees & affordable student loans for living cost OR no loans, and in the latter case, you already exclude based on wealth, so you might as well just charge whatever it is you want or whatever artificial treshhold you would like to enforce.
And you would be earning a fraction, say $120 per month, that automatically makes the 5k college dream, a dream.
That's impossible, because around here the minimum wage for an adult working a full time job is around 10x that figure.
That's because in some countries you won't be paying more than 5k to go to a decent college.