Difference between values in sales order cost estimate and the values posted to COPA

Dear Experts,

I want your help that I create a costing key for sales order cost estimate and assigned it to material types and I run the cycle from sales order > Production Order until billing but when I review the values in sales order costing and COPA document I found difference in every cost component.

by the way my operating concern currency is EGP and company code currency is USD , I doubt that this difference because of exchange rate but I made COPA posting in the two currencies company code and operating concern.

So I need your help in this issue because its critical and I can't make COPA reports with these values

thanks in advance,

Nassar