You can get a full itemized bill. The only thing that isn’t fully broken out are elastic ips. We found that out because we were tagging everything for billing and those weren’t showing up correctly.
Mind you, it’s likely a bit more itemized than you want. Like you’ll see a separate line item for each price tier you paid for something, and things like ebs disks are all split out. It can be a bit…much.
I think you’re over exaggerating the effort needed for tagging resources. Between terraform/pulumi/cdk and the tag tool, it’s relatively easy to make sure everything is tagged. Doubly so if you have a finance department who’s literal job is to go through and do that (or ask you for help with it)