Back in the era of landline phones, AT&T calculated that around 70% of their cost was due to billing. People welcomed "unlimited calls with $X a month!" as a l

Back in the era of landline phones, AT&T calculated that around 70% of their cost was due to billing. People welcomed "unlimited calls with $X a month!" as a liberating innovation, but the truth was that the phone company was saving a ton of money -- and had priced them so that they were making even more by the vast majority of their customers.