Accessibility to universities and colleges is a big issue especially for people from lower socioeconomic groups and ethnic minorities. The high cost of required materials are another barrier to entry for those who already have many barriers -- both social and economic -- in their path.
If the materials are necessary for a student to complete the course, then it is only fair that they be priced as inexpensively as possible. A student has literally no choice but to obtain these items. Expensive items are an unfair burden for a student who may already have made big financial sacrifices to get to college.
Required course material should be kept inexpensive as possible to guard against exploitation and excessive profiteering. When students are told they must have a particular item for a course, they become a captive and vulnerable market. Unscrupulous suppliers may seek to cash in on the required status of their product by artificially inflating the prices and thereby inflicting unnecessary additional costs on already financially stressed students and their families.
The integrity of the educational institutions themselves is compromised by having expensive required items. The school may be seen as greedy, uncaring or elitist. The institution may be seen as being out of touch with communities. A school that requires students to buy expensive material just to be able to complete the course could be accused of not having the students best interests at heart.