cost saving

Taking some action that will stop an identified cause of cash loss.

We saved loads by microwaving the cat. Not only did we reduce our food shop bill, but we also had a hearty protein rich meal for free!

cost savings

Money saved through acting like a cheapskate. Typically, the phrase "cost savings" is used to justify the action.

Leah: "Let's order a pizza in and get a bottle of wine"
Matthew: "Let's make a delissio pizza and get tetra-packed wine. Cost savings."
Leah: "Loving the cost savings"