Sim Companies economy engine models buying behavior of the "general public". Selling properties of products and goods (such as apples, saussages, etc.) sellable in retail buildings are guided by the model. The economy engine's goal is to simulate behavior that you would expect in the real world. Understanding the buying behavior of the "general public" allows players to develop strategies that maximize their profit. This can be simplified by answering the question, how quickly can I sell goods given my price and current market demand.
Sim Companies is using polynomial function to simulate increasing selling time with increasing price. This article will look at the actual values the model uses for apples for demonstration. The first chart describes the relationship between selling time in seconds and retail price for normal demand (red) and extreme demand (blue).
Note: The current market demand can be seen in the encyclopedia or in the building that sells the product.
Reviewing the data, it might look like the easiest way to maximize your profit is to sell at higher price. However, employees of your retail shop (grocery store, gas station, etc.) are being paid while the store is selling. So, the longer it takes you to sell the product the more you spend on wages. Next chart adds the grocery store wages into the equation. The maximum profit retail price for an apple is $6.
Another way of looking at the data is checking how to maximize profit per unit of time, instead of unit of product. As players have limited number of retail buildings available, they need to be used efficiently. We can also plug in the base cost of one unit of apple, since it has to be produced and it doesn't come cheaply. The last chart assumes normal market saturation and production cost of an apple of $2.4 and displays the building profit per hour.