Managed Airflow Scheduler on AWS with "large" size costs $0.99/hour, or $8,672/year per instance. That's ~ $17,500 considering Airflow for at least non-prod and prod instances.
Building it on your own on same size EC2 instance would cost $3,363/year for the EC2. Times two for two environments, let's say $6,700. $4,000 if you prepay the instance.
That looks way cheaper, but then you have to do the engineering and the operational support yourself.
If you consider just the engineering and assume engineer costs $50/hour and estimate this to initial three weeks of work and then 2.5 days / month for support (upgrades, tuning, ...) that's extra $4,000 upfront and $1,000/month.
So on AWS you're at $17,500/year and on-prem you're at best $20,000 first year and $16,000 next years.
So the AWS only comes a bit more expensive - but the math is tricky on several parts:
- maybe you need 4 environments deployed instead of 2, which is more for AWS but not much more for engineering?
- maybe there's less sustaining cost because you're ok with upgrading Airflow only once a quarter?
- you probably already pay the engineers, so it's not an extra money cost, it's extra cost of them not working on other stuff - different boxes and budgets
- maybe you're in part of a world where good devops engineer doesn't cost $50/hour but $15 hour
- I'm ignoring cost of operational support, which can be a lot for on-prem if you need 24/7
- maybe you need 12+ Airflow instances thanks to your fragmented / federated IT and can share the engineering cost
- etc, etc.
So I think what OP was saying is that if AWS priced Managed Airflow at $0.5 per hour, it would be no brainer to use instead of build your own. The way it is, some customers will surely for their own Airflow instead, because the math favors it.
Does that make sense?