When designing a productized service define the deliverables at the beginning before you even have your first client for the productized service.
If you have a clear definition of what the deliverables are then your client knows exactly what he will be getting.
If you have a clear definition of what the deliverables are you can determine what the outcome for the client will be based on those deliverables.
If you have a clear definition of what the deliverables are you can determine the value of the productized service and therefore the price.
One note: Even if you have the deliverables defined at the beginning of the project you don’t need to let the client know. These can be a surprise when they are delivered which may add to the client’s perspective of the service.