The [bitcoin mining] machines ... are worth about $20,000 each on the open market. Today, all of the machines dedicated to mining Bitcoin have a computing power about 4,500 times the capacity of the United States government’s mightiest supercomputer, the IBM Sequoia, according to calculations done by Michael B. Taylor, a professor at the University of California, San Diego. The computing capacity of the Bitcoin network has grown by around 30,000 percent since the beginning of the year.