It’s cheaper if you don’t have constant load as you are only paying for resources you are actively using. Once you have constant load, you are paying a premium for flexibility you don’t need.
For example, I did a cost estimate of porting one of our high volume, high compute services to an event-driven, serverless architecture and it would be literally millions of dollars a month vs $10,000s a month rolling our own solution with EC2 or ECS instances.
Not surprised, my basement is 58-64F (~14-18C) year round, no matter how hot or cold it is outside.