North Korea’s only mobile operator, Koryolink, is about to hit 2 million subscribers, its CEO Ezzeldin Heikal told diplomats and NGO workers in Pyongyang this week. Koryolink launched services in North Korea in 2008 and took more than three years to sign up its millionth subscriber. It doubled that number in just 14 months.

That’s great for North Koreans—at least those who can afford a mobile phone. And it’s even better for Egypt’s Orascom Telecom Media And Technology Holding, which owns 75% of the company and enjoys profit margins of 80%. North Koreans can’t do much with their phones: international calls are banned, internet access is limited to “a walled garden of scrubbed content taken from the real Internet”, and calls and texts are monitored by authorities.

Just who are these 2 million subscribers? The service is available in Pyongyang and another 115 cities, covering 14% of North Korea’s territory and 90% of its 24.4 million people. But in a country with average incomes of between $80 and $170 a month, only a fraction of North Koreans can afford it.

One reason for the surge in subscribers may be the short-lived opening-up of services earlier this year. In what came as a surprise to many, Pyongyang allowed Koryolink to offer foreigners full internet access on their mobile phones at the end of February. The government rescinded permission for tourists a month later but allowed resident foreigners to continue using it. Data packs cost nearly $200 for 2GB and over $400 for 10GB, which is pricey by any measure. In any case, the number of foreigners in North Korea is hardly enough to account for the huge boost in Koryolink’s numbers.

Another explanation comes from DailyNK, a reformist website. It says that demand for cellphones has expanded beyond “the cadre class” to others, but that the paperwork and waiting times involved put many people off. In response, a gray market of sorts has emerged, with middlemen registering several phones in bogus names before selling them on for between $300 and $500. Not counting bribes, getting a phone the official way costs between $100 and $300, depending on whom you believe.

The larger explanation for North Korea’s mobile phone boom may lie in the country’s growing underground economy. A lengthy Economist report in February revealed a thriving black market for foreign goods, which has “produced a class of new rich who sometimes flaunt their wealth”. Even without Facebook, mobile phones are the world’s most popular way to advertise your status.