Question 

I am using an EC2 created with Windows with SQL Server Standard, but I do not want to use MS-SQL. If I delete only the MS-SQL program on the EC2, can I get the charges applied for only a Windows server? 

Answer 

The instance is billed based on the Billing code information in the AMI used when purchasing the instance. [1]

Removing SQL Server from Windows with SQL Server Standard does not change the Billing code.

Therefore, removing SQL Server from an EC2 ordered as Windows with SQL Server Standard does not reduce costs.

To reduce costs, you need to order an EC2 without SQL Server.

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[1] AMI Billing Information Field
https://docs.aws.amazon.com/ko_kr/AWSEC2/latest/UserGuide/billing-info-fields.html