The key to markets is the concept of voluntary exchange.

市场的关键是自愿交换的概念。

Voluntary exchange suggests that the price is there for a reason.

自愿交换表明价格存在是有原因的。

You both felt better off; that's voluntary exchange.

你们俩都感觉很好。这就是自愿交换。

The point is that markets are everywhere and most are based on voluntary exchange.

关键是市场到处都是，而且大多数都是基于自愿交换的。

Now, ideally the eventual result of voluntary exchange is that sellers can't make themselves better off without making something that makes buyers better off.

理想情况下，自愿交换的最终结果是卖方制造让买方富裕的产品，从而让自己变富。