Who said Economics has nothing to do with real life?  This article from the New York Times gives an economically rational view of that little thing we call Love.

I will disagree with the part about your ROI equaling your investment. Love, unlike a business partnership, is not and should not be a 50/50 deal.  There should never be a sense that someone is not doing their fair share, at least not in a readily measurable sense.  These things suit different people in different ways. The challenge is finding someone to match your way.