What other email service allows you to pay by the number of emails sent?

admin

Alibaba Cloud, AWS charge 1000 emails for RMB 0.8-2 per email,

Mailgun, SendGrid ... can only pay monthly 10 dollars to send 50,000 emails, too expensive.

Does anyone have other options that allow charging based on how many emails are sent?

Because we send around 500-800 emails daily and about 20,000 in a month, the 10 dollar plan is too expensive.