I understand it’s still hitting Route53 infrastructure, but I’m not using it, and it’s not commonplace to charge for NXDOMAIN records. Because of this, I’m unable to host at AWS (prohibitively expensive for my use-case).

It’s worth mentioning that DNS infrastructure for things like this are very cheap (I used to self-host the DNS infrastructure for this domain for ~$2.5/mo), so the up charge is even worse that what AWS is charging for bandwidth. If they brought it in line with actual costs, I wouldn’t have as much of a problem.