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.

Of course, self hosting in our own data center is even cheaper, where we can buy and run new hardware that we can run for years for a fraction of the cost of even the most cost-effective cloud solutions, as long as you have the people to maintain it.