The National Bureau of Economic Research published a Working Paper “Why is Match cheaper than English? Understanding Cost Differences In Higher Education”. The study is based on data from the National Study of Instructional Cost and Productivity from the University of Delaware (the Delaware Cost Study), which has collected program-level data since 1998 from over 700 higher education institutions and some 22,000 programs in the US. The study shows that Engineering programmes are (109%) more expensive than English programmes, but Math programmes are 20% less expensive.
Part of the explanation is the difference in class size and faculty pay, though in some fields IT helps to offset higher salaries. Also, it shows that online instruction is associated with a modest reduction in cost per student, but only for undergraduate instruction.