I was lucky enough to be a student in the 1980s, when fees were paid and there were still (means-tested) grants available. Therefore, runs an argument beloved of the current teenage scribblers, I am in no position to comment upon either the current state of higher education or the fact that universities are likely to charge the highest level of fees that they can get away with.
The vast expansion of post-18 education that has occurred since my time was primarily driven by the need to drive down the numbers on the dole. Yet an expansion from around 10% to 50% of the population in higher education creates a totally different beast to the system thirty years ago - it's now a sausage machine, and probably better described as consisting largely of remedial teaching to bring people up to basic standards of literacy and numeracy. I'll say nothing about social graces as that would be very unfair.
There is some merit in the argument that graduates will probably pay more in tax than non-graduates over their earning careers. However, that does assume that the number of highly-paid jobs increases at least partly in line with the increase in the number of graduates.
If you view, as this government appears to, higher education as a means to an economic end, then there is a strong logic to testing the desirability of degree-level qualification through a fee structure that encourages people to think about the risks they are taking before they go through with their UCAS forms. It may reduce the numbers of marginal students for whom "uni" is three years of semi-hedonism to which they have a right, and in turn this may reduce the number of universities - which is a good and efficient economic solution!
There is no magic formula that provides a percentage of people who should go to university - and the delusion that the higher education sector is peddling is that there is never a time to row back. The real tragedy has been the blurring of insitutional boundaries - instead of the universities, polytechnic and college model everywhere is competing for university status (and the weaker institutions are peddling what can charitably described as a delusional equivalence with the stronger ones) - and the idea that only a seemingly-academic qualification is worth having. For many people it is, but it also creates expectations and fails to recognise what the individual needs is the building block, not shoe-horning everyone through a lowest-common-denominator education system.
There's the liberal education argument as well, but enough on this for now.