The $15 "1st Generation AWS IoT Button" is out of stock, but the $20 "AWS IoT Enterprise Button" is still in stock. Is there a difference besides the label?
The AWS IoT Enterprise Button is for the AWS IoT 1-Click service ("Trigger AWS Lambda functions from simple devices"): https://aws.amazon.com/iot-1-click/
Notice how the Enterprise button listing (https://www.amazon.com/dp/B075FPHHGG) says "This is not the AWS IoT Developer Button" with a link to the other button.
1) Double the lifetime clicks (2000 vs 1000)
2) More tightly integrated with the AWS IoT 1-Click service. (so arguably more restricted, but actually easier to manage and scale if you're an actual enterprise managing thousands of these in the field, rather than one developer building a toy app)