Their costs for Zerglings, Roaches, Hydralisks, Banelings and even Ultralisk is acceptable. The Mutalisk is ok and the Corruptor would actually be useful if it costed 25 less gas.
The Broodlord is spawned from the Corruptor and costs around 100 minerals and 150 gas, which I think is acceptable if they reduce the gas cost of the Corruptor.