We want to understand the pricing of sending SMS using SNS and what is Variable Pricing for Amazon SNS SMS Notifications to Rest Of World (non-US)?

This is available in the AWS website and FAQs

The pricing depends on whether you want to create a dedicated long code (10 digit number for US) or a short code (4 digit number for US) and how many SMSs you send. you can calculate the cost for each country you need to send to by looking up each country. There are specific restrictions to send messages to Singapore, US and India. Check those out to comply with regulations and incur the best cost.

NOTE. This pricing is only indicative. The price not fixed as AWS has to contract this service to a telecom service provider. As per their T&C, they can change the price with a short notice or even without notice. I would suggest to send test messages and observe the cost of usage - It takes 24 hours for the SMS usage report to be available in the S3 bucket.

NOTE: If you are an enterprise customer, please contact your TAM.