Thanks for the question. There are many reasons and theories about why college is so expensive: inflation, ease of access to federal student loans/aid, schools building facilities to attract students (such as huge gyms with rock climbing walls), compliance costs, administrative bloat, and on the list goes.
There are a number of things you can do to lower your cost of attendance. First, it is important not to be scared off by the "sticker price" the cost of tuition you may see on the colleges website or sites like U.S. News & World Report. What is most important is the "net price" which is the total cost of tuition once grants and scholarships have been applied. Many, many colleges offer grants and/or scholarships to students to help them lower the cost of tuition.
Aside from that you should consider:
Community College: Still one of the best values in higher education. Most community colleges have transfer agreements with other schools to help make your transition to a 4 year school much easier.
Alternative credit options: These include AP exams, CLEP exams, and options such as Straighterline which offers a low-cost course completion alternative with partner schools.
AP exams: https://apstudent.collegeboard.org/takingtheexam/ap-calendar
CLEP exams: https://clep.collegeboard.org/exam
In addition, many schools are reducing tuition rates and many others also have what's called "tuition lock" which means your cost per credit hour will not increase as long as you remain an enrolled student. You can learn more about those things here:
Tuition reduction: http://www.usnews.com/news/articles/2015/09/17/colleges-plan-to-cut-tuition-by-nearly-half
It's a lock to take it, but take it slow and explore as many financial options as possible before you enroll in any school.