Quizbank/Cost-benefit analysis/The economies of scale

The economies of scale play a crucial role in understanding the value of an open exam bank. Existing exam banks are either written and maintained by individual instructors, or are provided by vendors of a textbook and/or Learning Management System. This creates something akin to the cottage industries that prevailed before the industrial revolution: Many individuals are all doing the same thing on a small scale. In contrast, OER and numerous other online sites such as the Khan Academy provide instructional material to a vast audience at zero cost.

This focus on standardized tests for accreditation raises serious pedagogical questions that cannot be dismissed. But partial answers to these objections can take one of four forms:

Not doing something about the cost of higher education has serious consequences.
An enlightened and sparing use of the bank can help focus educational resources on the students who need it. Instead of excluding students from a course if they fail to pass the preliminary exam, open up small sections for those who need help. Offer alternative assessments such as essays for those not adept at standardized tests.
A zero-cost OER bank will exert downward pressure on what the commercial vendors charge.
Problems and exam questions are so abundant on the internet that the open exam bank effectively exists right now. Just a few minutes of searching the internet uncovers ample evidence that "the cat is out of the bag":

These are the legal banks. A GRE practice test and a 600 page exam bank from a well-known college physics book are currently available online. I believe both are copyright violations. The question isn't whether there should be a large public bank of exam questions and solved problems (it already exists), but whether this bank should be structured so that instructors can conveniently use it.