I actually quite like the system we have in the UK.

Graduates pay roughly 9% of their income above £27k towards debt repayment, and the remaining balance is written off after 30 years. Typical tuition fees are just over £9k per year.

This strikes a nice balance between encouraging people to carefully consider alternative non-university careers whilst also not preventing too many people from not being able to afford it.

Note my numbers are approximate because they can vary depending on when & where a person went to university a couple of other factors. Also I do think the system could be slightly improved (especially around maintenance loans) but on the whole has a good structure.