Teju Cole said this quote

Money, dished out in quantities fitting the context, is a social lubricant here. It eases passage even as it maintains hierarchies. Fifty naira for the man who helps you back out from the parking spot, two hundred naira for the police officer who stops you for no good reason in the dead of night, ten thousand for the clearing agent who helps you bring your imported crate through customs. For each transaction, there is a suitable amount that helps things on their way. No one else seems to worry, as I do, that the money demanded by someone whose finger hovers over the trigger of a AK-47 is less a tip than a ransom. I feel that my worrying about it is a luxury that few can afford. For many Nigerians, the giving and receiving of bribes, tips, extortion money, or alms--the categories are fluid--is not thought of in moral terms. It is seen either as a mild irritant or as an opportunity. It is a way of getting things done, neither more nor less than what money is there for.