The problem is how bullshit transactional emails are when you're outside of AWS. If you're not expecting to use 10,000 emails a month but would like the option to go over the free tier without committing to 10,000 more. Just let me pay per use FFS.
Scaleway TEM offer pay per use. I moved off of resend when my side project went beyond their free tier and now pay <0.5€ a month
The reason AWS does that is because there is a lot of base level work to verify you as "not a spammer" and to keep verifying you. So this is their way of making sure you pay the base cost.
They could price per use, but it would have to start with a base fee that is about the same at 10,000 emails.