Product pricing calculation goes wrong

Dear all,

I have define price for a product in the product page as below :

Standard cost = 1509
Current Cost = 1590
List price = 1810 ( current Cost  + 20% )

Then I go to my price list to add new product. From the price list I set my product price as Percent Margin of Standard Cost and then I set the % value to 20 , which should then give my 1810 final price

Then what is happening is that when I add the product to my opportunity the Price Per Unit field shows 1887 instead for 1810  !!!!!

What is the trouble with that ?

Did not get that trouble before, I do not know if it comes from last update

Thnaks for help