I feel like the entire framing here is the problem. You cannot see “The Thing” because you are looking at it from a perspective where The Thing isn’t apparent.
What is The Thing? It is having a partnership that you are both committed to. At its best this partnership becomes an aspect of your self, and your partner. The frame to see this in is that the partnership is an entity in its own right and is a part of the “I” that each partner identifies with. In this frame the question “what am I getting out of this relationship” is no longer entirely focussed on the individual “I” but also on the partnership “I”. When you frame the question in terms of what the individual “I” gets out of it then you are entirely missing the point and are unable to see the real value proposition.
If we dip our toe back into the individualistic frame: you could describe the value of relationships being in the partial dissolution of self in the partnership, which not only feels amazing but also gives a deeper level of meaning to your life.
If the economy is so easily understood then why do we have high inflation, a cost of living crisis, rising inequality?
The thing that is not understood is why these things are happening and how we can change things so that normal people are better off.
The fact that some people have some coherent theories for some aspects of the economy is not equivalent to us understanding the economy.