Data Usage Information of the Arduino SIM - Again

This is the title of a question raised by @mbatalla in Apr 2020 - unanswered though.

We need to know what the transmission overhead is to send a payload of data to IOT cloud.

5Mb is equivalent to 116 Bytes /min over thirty days. I would like to send about that much in the payload but initial measurements indicate that the overhead is MUCH greater.

If so it makes the use of the Arduino SIM useless. Comments please from Arduino?

I have a setup that connects and updates an integer value once every 10 minutes. According to my SIM provider it uses approximately 0.8MB every day, so about 5KB for each full sync. Way too much for the Arduino SIM's 5MB monthly limit.

I've been unable to find any documentation on why this is so much more than an equivalent MQTT setup.

In order to make relevant information easily accessible to interested parties, I'll add a link to that topic: