Why do markets need both adequate competition and adequate information?

Let's think about you want to build your home. You know 3 constructors who can build your home as you want to. But the price rate vary to each constructors. so made a tender and call these 3 constructors to join. At last they present their rate to build your building. Here is the question that who would you choose? You must choose that constructor who present the least rate for that tender. And you select the ONE. so you take a competition on three of them. that's why market need adequate competition. So you done it by lower price. It is a important terms that highly executed in business world. Think you want to buy something from another company but you don't know about that product. It means you are ignoring the fact that your money is under a good deal or bad. you have no interest about your money. but you are doing business for the money. so that you need that adequate information for that product. nothing else...