"...and can cost over $30,000 per year!!" [emphasis added]
Yes, they can, but most aren't anywhere near that sort of level, especially if students study instate.
Take California for example, tuition fees at California State University (CSU) next year are $6,084 (£4,515) for in-state students - rather less than the tuition fee in England.
For those at the University of California (UC) it is rather higher, at typically $14,934 (£11,084) but it does vary by campus.
In addition, UC offers a lot of financial aid and, they say, that 53% of UC students who are Californian residents do not pay any tuition.
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Or somewhere like Texas you will see similar things. Texas A&M University has tuition fees around $6,200 (£4,600) and the University of Texas has tuition fees from $8,700 - $10,900.
Now, of course, these are just tuition fees (the same as in the UK) and living expenses, rent, books etc are all on top.
Adding up all these extra living costs will very likely get you to $30k (the US is a lot more expensive than the UK).
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So how do students pay for their loans?
Well, there is something called "Federal Student Aid" (FAFSA). This works in a very similar way to the Student Loans Company in the UK.
The only real difference is that the amount of the loan takes no account of the parents income and the loan is repaid like a normal loan rather than how it is here now which is effectively an extra income tax.
In addition to this, many universities offer financial aid to local students so that they don't have to pay tuition fees.