Utility
Social Exchange theory can be seen in every single relationship that we have and it is seen in places that you might not have expected, like public relations. If you are trying to promote a product, you need to build a relationship with the he target audience. When the target audience feels as though they can trust you, your product will seem more useful to them, in which case they will want to buy your product and feel as though it was a smart decision.
Another place we see Social Penetration Theory is when we form romantic relationships with partners. When we start new relationships, we go through stages of getting to know a person and use the reward-cost ratio to decide whether or not someone is worth pursuing a relationship with. If we do not enjoy someone's presence or agree with their values, we will not pursue that relationship.