When going over the system settings in Dynamics CRM 2013/2015 you might encounter something called “Set pricing calculation preference” (you can find this under the “sales” tab). As the description states: “use system pricing calculation”, a user might be curious to what this does.
Well, the explanation is simple, these settings will decide whether the entire system (entities like quotes, orders and invoices depend on this) will calculate prices automatically or not. If you have been wondering why your order items do not show the right price and as a consequence why your order is not correct, this is the source of your problem.
EDIT 2015-03-03: To use custom pricing, select No for this option. Additionally, you must register a plug-in on the CalculatePrice message, provided in the CRM Web services, that contains your custom pricing code. Every time you create or change the product information in an opportunity, quote, order, or invoice, the custom code is invoked instead of the CRM system pricing engine to calculate the prices. (Source: “Administering CRM 2015 for online and on-premises”-Guide)