Return On Investments, relationship style

In business the ever-popular term Return On Investment (ROI) is almost always used in a question: What is my ROI with XYZ...?
When I hear this commonly over-used work abbreviation it makes me wonder, why shouldn't we evaluate our relationships on the same scale?
We all know you have to "put in work" when starting a relationship, but what if you put in too much and the relationship fails? Or what if you don't put in enough and your growth is minimized? OK, maybe I have work on the brain, but let me put this in context - AKA a story!

I have a friend; she's smart, successfully, cute, kind, and a little quiet. She carried on a relationship with a seemingly interesting male for several months. Time investment. She compromised her better judgment by engaging in late night meet ups. Investing in opportunities. She spent time ruminating and contemplating over each mixed signal, always hoping and considering the best-case scenario and ignoring the red flags. Bad investment... So when this not so awesome male figure ended up admitting to still being involved in a serious relationship with an old girlfriend and deemed himself emotionally unavailable, but anxious to keep her on his team, the relationship bank officially ruled: no growth or opportunity in this relationship, negative return on investment.
So what happens when you put in all this work and no benefits come of it? Is it no wonder relationships have transformed from courting to dating to sexting? Know what you're in for is today's mentality and it's all for the sake of saving your investment and energy for one person who really deserves it.  And no, this isn't something my friend expressed, these are situations that happen to everyone and unfortunately (or fortunately) the longer you are with someone leads you to a similar logical question of value or ROI: "is s/he worth it?". From a relationship perspective, begs a deeper answer from the heart and mind coming together to form a conscious decision. Often, the positive or negative answer to: if I give my all-will you be the one I love?
Similar to what I advised my friend, anyone who you feel is taking more than they can give is on the bottom part of the worth scale. Anyone that can try and make you feel less than YOU are worth doesn't deserve any investment, time- opportunity or quality. However, I do believe, there is a tendency to test to true value of a relationship. And there, comes a point in any relationships when we have to stop testing the worth and appreciate the value-otherwise you spend all your time analyzing the investment and never enjoying the benefits.