Example with a context (Students Use Clickers to Help Guide College Lectures):
Unfortunately "buy" is exactly what the students have to do on most campuses. The clickers cost around $25 each, and in most cases the students purchase them along with their books. But since there are several programs available, mostly offered by text book publishers, one clicker will not necessarily fit all.
So if a bunch of profs are using different programs, it may be necessary to buy several clickers, thus running the exploding education tab up for the folks back home.
I don't think I understand what that means.