When someone signs a contract, they agree to pay a price for the task done, if you use opensource or not, if product works as expected one is fine. You are using opensource to make your life easier so you should pay from what you earn. If you charge me extra for open source, what would be your reaction if I say don't use opensource write everything on your own. It is hard but fact is that I am paying price to something what I need from you. If you need some open source why not pay your self.
Infact as a developer someone else is doing what you are supposed to do if that doesn't exist you would be doing yourself
I challenge you (or the hypotetical company from your comment) to put on the table that constraint: Don't use OS at all.
Go with this constraint to ANY DEVELOPER and you will see how you run out of budget before day 1.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.