Human interactions, at a certain level, are like a negotiation. The other party makes an offer, you accept it or reject it, and in the latter case he may either make a better offer or let you walk away.
If you want to make a deal that is extremely in your favor, and insist on it, most people will not want to do business with you. You’ll have a very limited pool of business partners to choose from. Few people will want your product so badly that they will buy it at any cost.
If you want to do business with party X at any cost, you will be taken advantage of unless the other party shows mercy on you. Some business partners will, while others will prefer to set up an exploitative relationship. In any case, you are powerless to avoid exploitation when you are at the mercy of others. Healthy people do not like to be exploited. They have a sense of dignity and exercise their boundaries. So if you sell your product too cheaply, you’ll end up with business partners who lack mercy. Yet if you insist on exploiting people, you’ll end up with unhealthy people who are used also by others untill they have no use anymore.
Socially, it is much the same. If you want to have relations that are enjoyable and beneficial over the long-term, having healthy people in your circle is key.