Not sure why you didn't click on "Billing & Cost Management" where you can see a complete breakdown (by resource and region) of exactly what you are being charged for.
I don't know about the previous commenter, and I don't know if the tools have improved, but when I tried to use the billing and cost management page, I couldn't figure out what was actually costing so much. It broke it down into (EC2, S3, etc.), but I couldn't figure out how that mapped out to the bill (i.e. was it the snapshots of my instances, the storage for the not running instances, the old backups in S3, etc.). It didn't seem like it was telling me "exactly" what I was being charged for.
For me, when I saw a $300 bill for one running EC2 instance, a couple of halted ones, and a few hundred GB of storage for something I thought of as a "toy" project that I didn't want to invest serious time or money in, I knew I was done with AWS. A small colocated server could readily provide those resources for vastly less money (and I work on tools to manage cloud and VM resources, including a reasonably good API for spinning them up and down and such, so I don't really miss the Amazon API or UI). This was after I'd already gotten a shock from an automated backup gone wrong that ran up a huge bill. So, it took me a couple of times getting burned.
Of course, it's always been my fault for not understanding how Amazon bills for things, what services cost money (i.e. a down instance still costs money), how much things cost, and sometimes how the API works (or at least confirming that it's doing what I think it's doing, in the case of removing old backups). I'm not blaming Amazon. I'm just saying, I don't trust myself to use Amazon for anything that I'm not going to spend a lot of time and energy on, because I'm obviously not capable of using it without making mistakes when I treat it like a toy. I readily admit I shot myself in the foot; Amazon just provided the guns.
