Best way to generate a project quote without sales price

Hello

A customer wants to generate project quote without sales price, he only wants  to have (calculate) the costs for some resources roles without sales price -> once he has an idea of the total cost price, he needs to apply a coefficient to calculate his final offer price

Ex :

- 10 hours of developper * cost price : 50 € = 500 €

- 10 hours of PM* cost price : 70 € = 700 €

TOTAL  COST 1300 € and then apply his margin coefficient on this total

Any idea is welcome. I already tried with a sales price at 0€, but that is not clean...