Yes, they are interesting ideas @micheleminno. Very complex in many ways, but - as you say - a lot of the groundwork is being done in a large number of projects.
With the regards to the pricing - the concept that you pay for the loss of value of your profile - is a very innovative idea. It is the opposite of the much-talked-about selling of your own personal data. This last one is discussed now and then on Hacker News. The consensus is that it is probably not attractive for users to do this, as there is so little money to be earned (your prices are in the correct range), and your most valuable data (name, address, phone, etc.) can only be sold once.
When you turn it around, it is a bit easier, more feasible. It is very hard to accurately determine price, though. But the social network could set the price using their own price models.
A thing to consider: If I want privacy guarantees, why wouldn’t I go with a social network that offers a paid subscription model? – though you are probably thinking of a model that would be acceptable to the big tech platforms, like FB.
The biggest issue, I think, is enforcement. How do you check whether the social media network provides all the aggregated data? And once they sell the data to 3rd parties, how do you still have any control over it? How do you know what was sold?
Answer is, you can only enforce with proper regulation, and goverment + the law + high fines for breaches of contract. Interesting in that regard is Estonia, the most digitalized country in the world, where you can do all your government services entirely online, except marrying and buying a house. They have created a framework of laws to support their digital services.
And another thing that is interesting, is the initiative started by Tim Berners-Lee - the founder of the internet - and his Solid framework. Contrary to what Estonia offers and to your idea, this technology is decentralized, but still gives you control of your own data. After long preparation there was a launch last month and first commercial initiatives have started. See: https://solid.inrupt.com/how-it-works and https://solid.mit.edu/