Pricing is certainly both an art and a science.
Pricing is a science because it is based on some objective numbers. A price should be based to some degree on the costs incurred in the creation of the item being sold. To this extent, it is a science.
However, it is also an art. For example, it is necessary to decide how to price items at various times. People who make decisions about prices have to think about when to put a given item on sale. They have to think about when to include it in various kinds of promotions. They have to be able to have a feel for how to change prices in order to get the highest overall profit in the long term.
In these ways, pricing is based both on objective numbers (making it a science) and on intuition (making it an art).