I think the pricing model for Revue has changed since Twitter purchased the platform. I can't seem to find a pricing page any more, and they take a small percentage from membership payments. They don't say the exact amount but it does seem less than Substack.
EDIT: I have just found an article on Revu’s help section. They charge 5% on all memberships fees which is cheaper than Substack’s 10% charge. http://help.getrevue.co/en/articles/4635935-why-should-i-use-revue-and-not-substack-or-another-service