Attribute price that is not multiplied with quantities

[freuxbang]

Hello everyone,
How can I associate a price amount to a combination that is not multiplied by the selected quantity?

I have a customizable product, with different combinations.
Among these combinations is an attribute called "Graphic Review". The impact that this attribute has has to be calculated only once and not multiplied by the selected quantities.

Product price 10 €
Selected attribute + € 5
Quantity 10

The result must be this:
(10 * 10) + 5 = € 105

Currently how prestashop manages the attributes the result is this:
(10 + 5) * 10 = 150 €

Thanks in advance.