The difference

This indeed confused a lot of customers. After all, they were all tomatoes and cucumbers why was it that one shelf could be bought with three hundred cents, the other at five hundred and the final one was marked at two taels a catty? 

Li Wan and the rest who were aware of the prices also turned to look at the shelves which had vegetables sorted neatly. They knew what kind of prices Yu Dong usually set and were thus quite surprised when they saw that she had actually marked the prices of vegetables of the same kind from low to high. What was happening?