Why is college so expensive?

Because colleges/universities need to pay for professor, staff, buildings, water, electricity .... and tuition is one of the main sources to pay for this stuff.

What you need to do is:

1) Apply for scholarships.
http://www.collegedata.com/cs/search/scholar/scholar_search_tmpl.jhtml
https://bigfuture.collegeboard.org/scholarship-search

2) Maybe get an on-campus job.

3) Apply for paid internships during the summers.
http://www.internships.com/
https://www.looksharp.com/

4) Apply for Student loans.
https://studentloans.gov/myDirectLoan/index.action