Americans discouraged by higher gas prices and airline fares may decide to spend more vacation time at home, perhaps watching television. But that, too, will cost them more than ever. Cable prices have risen 77 percent since 1996, roughly double the rate of inflation, the Bureau of Labor Statistics reported this month. Cable customers, who typically pay at least $60 a month, watch only a fraction of what they pay for — on average, a mere 13 percent of the 118 channels available to them. And the number of subscribers keeps growing. The resiliency of cable is all the more...