Service are equations.
Customers and service providers are equated in terms of the outcomes and experiences. Each sides puts in time, money and effort. Feelings and emotions perhaps. Tangibles and intangibles. Experiences are part of what each side puts in. Outcomes are what they get.
Customers receive a payoff usually in terms of the results and benefits of whatever job the service gets done, such as the transferring funds, the issuing of a permit, the daily supplying of electricity, or placing in orbit of a communications satellite. Service providers receive a payment, directly or indirectly, in cash or in kind.
It is quite obvious users go through the experience primarily defined by dialog and interaction they have with the staff, facilities, and infrastructure that are part of the service. Agents, acting on behalf of the service enterprise, have a corresponding experience.
The design of dialog and interaction aims to minimize the cost of engagement and fulfillment. In services, experience is a transaction cost. Improving the experience results in the lowering of transaction costs.
Even the simplest of services is a closed-loop system. What goes around, comes arounf. The demand side of the equation balances out with the supply side. We learned how to balance equations, in physics, chemistry and math. The same is with services.