The revision cap is a pricing tool
Two rounds and one consolidation rule change the shape of a project.
Unbounded review is unbounded cost
A project without a revision cap has an open end. The price is fixed but the work is not, so every extra round is a discount the client did not ask for and you did not agree to.
Define a round precisely
One round is one consolidated set of comments, delivered once, within a stated window. Scattered comments across three emails are either consolidated by the client or treated as separate rounds. Writing this down removes the most common ambiguity in reviewing work.
Price round three
Publishing the price of a third round does two things: it makes the cap real, and it gives the client a way to buy more without renegotiating the project. A cap with no price is a threat; a cap with a price is a menu.
The consolidation rule protects both sides
It protects you from drip-fed feedback and it protects the client from a vendor who counts every email as a round. Put the window in days, not in vague wording.