[HatchedLake721]

Emmm, no? You can download detailed billing and drill down if you want.

If you see differences, one reason is that with hourly billing your monthly bills will be different, depending whether it’s a 28, 30 or 31 day month.

[justin_oaks]

I've been with AWS for a number of years (personal and for work) and haven't seen this problem either.

Some services will be higher if you don't account for all the costs. You can do the math for an EC2 instance but if you don't account for storage prices and bandwidth prices then the bill will be higher than you expect.

But some service prices will be lower than you expect. If you create multiple EBS snapshots from the same server, you'll notice that the price you pay isn't the sum of the individual snapshot sizes. It's far less because each new snapshot only saves data from blocks that have changed since the last snapshot.

[tyingq]

For people just starting, I can see it being true. A pedestrian example might be a Lambda. You look at the pricing on their site and calculate it down to the penny, but the cost ends up higher. Because the Lambda pricing page doesn't mention the Cloudwatch logs that were created with your Lambda, but they aren't free. (Leaving free tier stuff out of the picture).