RDS for MS SQL DB Instance Upgrade

From the calculation, it seems you selected Reserved Instance. There are few variables that you need to be considerate of while creating an estimation:

• Do you have t2.medium reserved instance right now?

• If not, then would you prefer to purchase reserved instance or would like to keep it on demand. With reserved instance, AWS would require commitment and irrespective of your utilization, you'll be charged for that commitment. Refer AWS Reserved Instance Pricing for more details.

• Is your existing database multi AZ?

• Is RDS proxy needed for your use case?

• How much storage do you have right now in existing database and how much would be required anticipating future requirement?

From your question, it's not clear whether you are looking for price comparison or you are faching challenges in upgrading the instance from t2.medium to t3.xlarge.

1. If this is about price comparison, then I'd suggest you to check your bill or cost explorer to see how much your existing DB is costing, then compare it with your price estimation with t3.xlarge instance. This way, you'd know exactly, how much it would cost additionally. Or you can Add service in existing estimate and enter configuration details of existing DB instance t2.medium, that way, you'd be able to see the difference.

2. If this question is about, how to upgrade instance from t2.medium to t3.xlarge, refer Modifying RDS DB Instance.

If this doesn't answer your questions, could you please comment here to clarify it little further.

Abhishek

goto aws pricing calculator or any third party web application, you can compare the pricing and estimated cost and keep in mind if you're using "on demand" you cannot calculate exact amount but for any other reserved instance then go ahead.