Thus, if your manuscript is rejected by any of the other 50 journals of ACS due to poor novelty or impact, you will be asked to transfer it to ACS Omega. You can pay and publish (assuming, of course, that your manuscript is scientifically sound). Read about the discussion here.
I am sure that many authors from India will pay from the CPDA grants for these open-access journals. After all, they are published by Nature and ACS.
This is not to be confused with RSC advances, which requires significant advance and impact. RSC advances started as a transfer journal for RSC but immediately rose up the ranks. In 2015, it received more than 50000 submissions and accepted around 25000 papers and published 100000 pages. The reason for the large number of submissions to RSC advances is because it is NOT open access.