Costs are always ex ante. There are no such things as social costs or social benefits. Costs are determined by how much entrepreneurs think consumers will pay. Costs are not determined by supply and demand. Nobody waits for costs to raise prices. Rothbard does not believe in cost curves.
Antitrust suits are often filed by one set of competitors trying to eliminate another set. Additionally, antitrust suits are money making rackets for lawyers.
Interest is not just a loan; it is a time preference. Usury laws misunderstood interest.
Part four of seven from Introduction to Economics: A Private Seminar with Murray N. Rothbard.