When staying physically or in a different kind of connection with a person or a group of people who are disregarding your wellbeing the cost is incredibly high.
The cost of staying when you are giving and never get anything back is the cost of your self respect. Not respecting yourself is opening the gate to : addictions, dysfunctional relationships, abusive consumption of foods and drinks, emotional abuse and physical pain.
When the person in front of you feels like a wall, closed, on guard, requesting and not giving, not exchanging emotions and thoughts, never saying "sorry- I made a(nother) mistake" the cost of staying is your mental and emotional sanity.
The cost of staying when, in a dedicated relationship, your partner is all over (un)social media, giving attention to all the other men/women who are also hanging there, always busy or going to all the other places a person can go to, but not there where you can be together - the cost you are paying is counted in time, in unique lost days which are never coming back. Time could also be seen as life energy never getting back. Not during this lifetime at least.
The cost of staying when at work you are being used and anything you do is not good enough - this fact being "exposed" as a personal failure, you are not getting support and encouragement, the cost of staying is your confidence.
You need to become the kind of person who is supporting and is receiving support.
The cost of staying in a relationship when the person next to you is deflecting ( confusing someone by setting them off course with abstract or incoherent reactions) and reflecting their confusion back to you, in fact refusal to be present, the cost you are paying is your trust, trust in yourself and human community.
The cost of staying is your heart and everything you can bring to life when being loved, supported, listened to, respected, understood and taken care of.
I cannot stress enough the importance of becoming aware of these costs.