These services are free. Many of these so called free services have a catch. Usually somewhere in the fine print of the terms of use agreement it will say they will share your usuage, information, and whatever they feel like to their “partners” and of course all everyone just clicks agrees without reading.
Our data may be worth something but we agree to give it to them in order to use their services. So they wont have to pay us.
It would be nice that shared the wealth they earned from us…
As to knowing what’s my data worth, a waste or time bill the government is working on. There’s others areas they can be focusing on. Besides knowing how much they make off me would be annoying