For service type workloads (e.g API service with 99.99% uptime SLA) we keep comparing on-demand vs. spot.

In reality, you would like to compare Reserved Instances as you can get 60% discount.

So in us-east-1:

- spot costs: 35-43% of on-demand

- RI 1 year standard: 60% of on-demand

- RI 3 year convertible: 46% of on-demand

So if you have some base load that you can commit to running for 3 years, the price gets often at spot range while not having to worry about losing capacity.

In-reality sometimes combining reserved for some base capacity 60% + 40% spot for spiky seems to be the winning combination for many companies.