Hi @ 寶貝 Greetings! Welcome to Microsoft Q&A forum. Thank you for posting this question here.
The Azure IoT Central Standard 2 tier comes with 2 free devices and each device can send up to 30,00 messages free of charge. You will only be charged for additional messages that the devices send in once the limit of 30000 per device is met. For additional 50000 messages, you would only incur a monthly charge of $0.75
Below is a breakdown of Pricing of IoT Central for different tiers.
You can calculate the cost estimate for your IoT Central, based on the devices and the messages count, through the following link - Azure IoT Central Cost Estimate. From the link, you can choose the Region where you are hosting the application and configure the devices and the additional messages to get an estimate. Please refer the following image for reference.
Kindly note that additional messages field takes message count in
millions
Hope this helps! Please let us know if you have any additional questions.
If the response helped, please do click Accept Answer and Yes for the answer provided. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.