Recently I saw a post about the Nigerian exchanges and i realized that the buying/selling rate there is 20-30{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} different that the EU and US rate.

That means that the people in Nigeria buy at +30{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8}, BUT that also means that the Nigerian exchanges buy at +25{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8}.

Simple math: Buy rate at BitFinex at 08:00 GMT = $915 Sell rate at Naira Exchange ar 08:00 GMT = $1149

That is a huge difference and it can surely be used for arbitrage.