If you are using the Shiptheory API to download shipment data, you may notice that when viewing the products on an order, there are both a value and a catalog_price field. 

value = The price of the product on the specific shipment

catalog_price = The price of the product in your Shiptheory account when not attached to a shipment.

Why do value and catalog_price differ?

For example, if you have 5 orders with the same product, "hat" in this example, priced at $10. But then a new order has a discount applied, and the hat is only $8, and then the next order the hat is $10 again. When viewing the first 5 orders and the 7th order, both the value and the catalog_price of the hat would be $10. But viewing the 6th order, the value would be $8 and the catalog_price would be $10.