Unit Behavioral Economics

In economics, the concept of unit economics is defined as:

the direct revenues and costs associated with a particular business model expressed on a per unit basis

I think there should be a term and concept BEFORE there is a business/revenue model. Something like:

the direct incentives, disincentives, and behaviors associated with a startup product expressed on a per unit basis

Before you have a revenue model, I'm interested in why a SINGLE user chooses to be on your product, and why not. I'm interested in how that SINGLE user interacts with your product - how frequent, how long per session, and why they churn. I'm interested in how old that SINGLE user is, what demographic, and how you would think about expanding to other users.