Financial aid is offered in the summers - you get aid for 8 in class semesters, no matter when you take them. A summer session is half of a full semester.
Co-op pay usually offsets room and board, and in some cases you even make money while on co-op, though that is dependent on your major. Some majors can pocket as much as $10k on a single co-op. For the purposes of considering the price, assume that during co-op you neither make nor lose money.
Basically, the cost is just like any other school - co-op does not make attending more expensive.
To be sure, triple check with the financial aid office and you can ask them any additional questions while you’re in touch with them in terms of affordability.
Hope that helps!