Comcast advertises very clearly that unlimited is an additional $50/m: https://dataplan.xfinity.com/unlimited/
Please tell me, how do I avoid paying overage fees? I have zero moral qualms about defrauding Comcast to the maximum possible extent.
It'll be paid. Most of their customers don't have any other choice but to pay it. (Otherwise, most of them already wouldn't be their customers, after all.)