This is great feedback, and initially I had a calculator for this. We removed it because we felt it would be intuitive but you're right we built it and it's easy to lose that outside perspective.

It's really just the running time of your program (you control this) plus a less than a second of setup / tear down time. If your job is set to consume 1GB that's it, you've consumed that many GB-seconds. If it's a 128MB job, then you've only consumed 1/8th of that many GB-seconds.

Let me know if this example is getting it across, it's a simplified version of the pricing of other serverless platforms.