since some of the components of the scale are metallic, they are prone to rusting which would cause error in reading of the scale so there is organized checking if the scale to correct that.
The price of many products in the market is "__ dollars per pound", or "___ rupees for 100 grams".
The scale in the market is used to measure how many pounds or how many grams the customer is taking home, and how much he should pay for it. Sometimes the scale is used to weigh the "money" too.
If the scale is not showing accurate weight, then the shopkeeper is either cheating himself or cheating the customer. Fair and honest business is not possible without accurate scales.
There are nearly 100 verses in the Bible regarding this. Leviticus 19:35 is the first one.
