Hi Giuseppe,
Yes, sure it's can be done with a Gridbox Store App -
Memberships and subscriptions
1. You need to create a specific Joomla User Group
2. For your blog posts set to access only for created user group
3. In Gridbox Store App create a product with a type subscription and in the Subscription Action set access to Joomla User Group - select created user group (step 1)
Regards,
Artem, Balbooa.com