I think that Bitcoin Magazine might be using the official exchange rate of about 460 Naira to the dollar.
Nobody will ever sell you dollars at 460 Naira to the dollar.  I doubt that even the Nigerian government would do that, despite the fact that it's the official exchange rate, because the Naira isn't worth anywhere near that much.
The Naira goes for about 750 to the dollar on the street, according to my cursory online searching.
I've never been to Nigeria nor exchanged Naira, but I've been to Argentina several times and exchanged money there.  The Argentine government will be happy to buy your dollars at the official exchange rate.  You will never in this life pry dollars out of the hands of the government at the official exchange rate.
In countries with weak currency, high inflation and capital controls, the official exchange rate is a complete fiction and merely a tool of financial oppression.
Unfortunately, some people will base their economic analyses on that exchange rate.
The question is, how much are people really paying for bitcoin in Nigeria?