I highly doubt you will have to pay this large bill, they most likely will reverse the charges and you should be free and clear, especially if you detail what y

I highly doubt you will have to pay this large bill, they most likely will reverse the charges and you should be free and clear, especially if you detail what you found and that you also have an email from them that your key was exposed. I for sure would go to your billing report on the AWS console and setup alerts. You can have AWS notify you automatically if your bill goes above any threshold you want to define.