The unit economics is a conveyor belt

If we can imagine a metaphor to describe the unit economics, a conveyor belt of customer service and revenue generation would be the best fit.  

In fact, the unit economics at the input receives potential customers who came from scaling channels, and further going through the looms of business processes such as conversion, sales, costs, retention - bring profit to the business.

And if this is the case, then as with any conveyor belt, you can apply optimization tools, such as Goldratt's theory of constraints, which will allow you to find points of business growth.