Measure Retail Sales Revenue output with existing cost based model

Hi,

I’m currently conducting an economic impact analysis for a festival, where I’ve developed an Industry Impact Analysis (IIA) that captures the output based on the industry’s total production costs (expenditures). The majority of the data for this analysis is derived from expenditure reports. However, given that there are retail activities at the event, I’m looking for guidance on how to accurately capture the value added from sales receipts without double counting the cost of selling goods and services already included in the IIA model.

The two approaches I’m considering are:

1. Excluding the cost of selling goods and services from the IIA model and creating a new commodity event using producer prices.

2. Keeping the cost of selling goods and services in the IIA model and creating a new commodity event with purchaser prices, applying a margin to prevent double counting.

3. Include the Revenue as Total output in the IIA model.

Could you advise on the approach to ensure accurate modeling?

Thank you.