This is extremely complicated. Candidates like Bernie Sanders want free public college but the funds for that have to come from somewhere (Senator Sanders proposes taking tax money from corporations and cutting their tax breaks). The reason other candidates are not proposing the same is because given the way our economy is structured, free higher education is nearly impossible.
That said, there are many ways schools could lower their costs. Many people cite overpaid administrators and coaches, unnecessary landscaping budgets, and useless technology as places schools could cut back. They could also not use expensive search firms to conduct hires. They could not contract with outside vendors to organize/support large-scale programs like study abroad programs. None of these suggestions alone would make much of a difference, but together they might make a dent in schools' expenses and thus lower the overall cost for students.
But instead, schools are relying heavily on part-time faculty whom they can pay a lot less and not give benefits instead of paying salary and benefits for full-time faculty members. The critique of this is that many professors with PhDs are not being paid living wages by their institutions. Schools are also minimizing their hiring and giving people raises. This has created an insular system where no one is retiring or being hired so there are few jobs in academia....which means colleges are having a hard time changing to meet the needs of 21st century students. Colleges are also admitting more full pay students to help supplement their overall budget. This means that fewer financial aid students can be admitted.
So long story short, we don't have any good solutions or proposals right now. The cost of higher education is rising quickly and fewer and fewer students are able to access college, especially private colleges (despite federal aid programs like Pell Grants). The rising cost of college in conjunction with a decimated economy has contributed to a stratified society. The best plan for families to be able to pay these exorbitant prices is to look for and apply for scholarships beginning Junior year of high school. Many colleges also offer very generous scholarships if students' GPA and SAT/ACT scores are at a certain level (and that level is not 4.0 and a perfect score by ANY means). The key is to apply and be admitted as early as possible (october or november) before the scholarship money is claimed.