Imagine you went to a pizza store and order a supreme pizza and then you received the pizza with the box. Looks like it is simple to make it, bread and cheese and other toppings. But, Do you know that owner of the pizza store has to deal with over 20 expenses to keep that pizza store up and running.
On the other hand , A pizza seller with a pizza truck goes to a store get a hundred pizzas from the store and goes to a festival. The seller starts selling pizzas with 8 dollars price at the festival. Some customers have no cash enough they want to make a deal with the seller , they give seller 6 dollars instead of 8, the seller is intelligent, he sold the pizza with 6 dollars price as well, but next customer has paid 10 dollars so it is 8 dollars pizza price plus 2 dollars tip. Actually what happened here is two different customers have balanced each other's payments. In the end, You still have 16 dollars in your pocket and happy customers.
Unlike pizza store, Students has only 6 different basic expenses to complete the college successfully in terms of payments.These are Tuition Fee, Accommodation Fee, Eating, Materials for Courses (Books Etc..), Transportation, Social Activities.
As we are in the research phase, we need to consider these 6 basic expenses and how they affect each other. Imagine a college makes 2000 dollars discount on Tuition Fee in 2015, this may have no meaning for you because your accommodation + eating + materials + transportation +social activities expenses increased about 2000 dollars at that year as well. So They balance each other like the trick made by pizza seller.
Finally, we can see that even the college is free , we still have few more expenses to deal with. Let's widen our viewpoint on the cost of college.