They didn't need to cover server costs for CS 1.6. I wonder why that is? Hint: CS 1.6 wasn't designed from the ground up as a microtransaction vehicle so could have servers run by the community unlike CS:GO where centrally run servers are needed to make microtransactions work, not the other way around.
A company choosing to take a loss on a service is not the same as not needing to pay for it, it was getting paid for.