I know of two use cases for this system: 1. There are races of cheap cars in UK, the prices of cars are kept low because everyone has to declare car value and

I know of two use cases for this system: 1. There are races of cheap cars in UK, the prices of cars are kept low because everyone has to declare car value and anyone can buy it at said price (this is intended to keep the prices low). 2. I do not remember where I read about it, but some medieval town near the river used this system for collecting taxes, any passing ship would be taxed on declared value, but tax collector had the right to buy cargo for declared price.