This is a significant amount of credit. Since it is not transferrable to a different account, how could you guarantee that this account would not be suspended? What would stop you from claiming your account had been hacked or anything like that?
Would you consider authorising the buyers account to "use" this billing account instead? If so would you consider taking payment in parts, for example in advance for every $1000 of credit used? That way there is less risk for buyers, and equally you can stop it at any time (by disabling the buyers account) if they don't pay.
Going rate for AWS is around $6-10 per $100 of credit, less if buying in bulk. I would expect a $15k account to fetch somewhere around $1000-$1200.
I think I could change the email and password after the payment so that shouldn't be a problem. I have an expired card on there but account is still active (has been for the past year or so) so I doubt that will really be the problem. It might get suspended if you will go against their TOS so I can't really guarantee that if you will let's say use miners for BTC on there as that will totally get it suspended.
Why would I do that? I have no use of the account and no means of scamming like I said this will go to someone that knows what he is doing and know the TOS of AWS as I don't want to see it go to waste even though I am not using it much anymore.
If possible I would like to sell it in one go but if that is something that would make it assured then yes can be done.
As for the price I was expecting to get somewhere between 1.5k (but can negotiate if you got a good reason to use this).
If you got more questions I will gladly answer them.
The list where the credit can be used:
AWS Certificate Manager
AWS CloudTrail
AWS CodeCommit
AWS CodeDeploy
AWS CodePipeline
AWS Config
AWS Data Pipeline
AWS Data Transfer
AWS Database Migration Service
AWS Device Farm
AWS Direct Connect
AWS Directory Service
AWS Elastic Beanstalk
AWS Import/Export Snowball
AWS IoT
AWS Key Management Service
AWS Lambda
AWS Mobile Hub
AWS OpsWorks
AWS Service Catalog
AWS Storage Gateway
AWS WAF
Alexa Top Sites
Alexa Web Information Service
Amazon API Gateway
Amazon AppStream
Amazon CloudFront
Amazon CloudSearch
Amazon Cloudcast (deprecated)
Amazon Cognito Sync
Amazon DynamoDB
Amazon EC2 Container Registry (ECR)
Amazon EC2 Container Service
Amazon ElastiCache
Amazon Elastic Compute Cloud
Amazon Elastic File System
Amazon Elastic MapReduce
Amazon Elastic Transcoder
Amazon Elasticsearch Service
Amazon Flexible Payments Service
Amazon Fulfillment Web Service
Amazon GameLift
Amazon Glacier
Amazon Kinesis
Amazon Kinesis Firehose
Amazon Machine Learning
Amazon Mobile Analytics
Amazon RDS Service
Amazon Redshift
Amazon Route 53
Amazon Simple Email Service
Amazon Simple Notification Service
Amazon Simple Queue Service
Amazon Simple Storage Service
Amazon Simple Workflow Service
Amazon SimpleDB
Amazon Virtual Private Cloud
Amazon WorkDocs
Amazon WorkSpaces
Amazon Zocalo
AmazonCloudWatch
AmazonWorkMail