I use to buy bitcoins through localbitcoins.com in my country, Argentina, and I noticed that there is an important gap between the buying and the selling price. This gap is around 200 ARS (~20 EUR). This way, if you want to buy/sell fast, you choose one of the available buy/sell ads. Otherwise, if you can wait, you can post your own ad with more convenient prices. Even further, you can post both sell and buy ads and make profit of the price gap.
However, when I was in Spain, I noticed that there was no gap between both prices. Why is that? Are they just good willed people who just wants to exchange coins and don't care about profit? Or is because there is more people posting ads and because of their competition prices tends to balance? Or is because another reason I don't see? It happens the same in the whole EU? What happens in other countries?