But those are not the fees the Gates foundation are going to pay. They are talking about the somewhat lower fees payable to open-access journals. E.g., some $20

But those are not the fees the Gates foundation are going to pay. They are talking about the somewhat lower fees payable to open-access journals. E.g., some $2000 for PLOS journals, if I remember correctly. What you describe appears to be the opt-in open-access option provided by commercial academic publishers such as Springer or Elsevier. If you ask me, this option is probably there so that they can say they accommodate open access; they don't really expect many researchers to pay them.