You could use other email providers. Fastmail, mailbox.org, runbox.com and more, plus all those who offer domains that include email. Instead of 6 USD/month/employee you'd then pay half. I'd argue company's highest overhead is salary, not spending a couple of USD/month for the most essential communication tool.
You are incorrect.
SES isn't a substitute for GSuite. It's a substitute for other mail delivery services like SendGrid or Mailgun -- a tool for programmatically sending emails, typically to customers.
This is applicable for mostly startups that don't have a lot of employees and this can help them cut costs to some extents in the beginning by not getting GSuite or other similar services.
- The company's admin on AWS verifies their domain on AWS SES.
- Employees create an account on GMail exclusively for work.
- Admin creates a Lambda function to map emails to employee email addresses.
- Each email address is verified and then SMTP server is set up.
I'm not saying startups should use this since GSuite is cheap in itself but in theory, this is doable unless I'm missing something and sounds like a good workaround I guess.