The American higher education system is, if you take a long term view, fucked. We're locked in a student loan bubble. Student loan debt levels are at an all time high. Something has to give. Now, in California, there's an alternate plan that (not to alarm you) just might make sense.
An activist group in California is proposing that the state charge graduates of its university system 5% of their income for 20 years after they graduate, as tuition. The LAT reports that it's not completely wacky: the head of the entire UC system has said that he likes the plan, and that his team will study it. In that case, let us do some quick and dirty math.
Current UC undergrad tuition per year: $12,192
Four year UC tuition costs: $48,768
Which would equal 20 annual payments of: $2438
Which is 5% of: $48,768
This means that if your average salary over the 20 years after you graduate was less than $48,768, you would save money by paying on this percentage plan. If your average salary was more than $48,768, you would pay more on this plan (although it's hard to say exactly where the line would be without knowing how interest and non-tuition expenses will be factored in).
Perhaps more pertinently: if your salary after college was approximately jack shit, you could save a lot of money on this plan, and be subsidized by all the fuckers that got rich, which is only fair because they're probably the ones who ruined the economy and caused you to earn jack shit. It's a good socialist plan. Let's do it.