Warning: between Antibes (Sophia) and Paris I would adjust salary value with a quality-of-life factor of about two.
The length-of-life factor, eg. air-pollution, city stressors, and so on, is impossible to evaluate.
I work in Sophia Antipolis too! I'm 33yo with 9y of experience and my current salary is 56k "brut". If you work for an SSII your best chance of a salary increase is to become staff in one of the companies you are contracting for!
Then you can move to Paris to have a better salary but you will also pay more for your life... You could move seriously, there are a lot of companies in Paris that are looking for developers so they will pay more than what you earn now.
I don't think you can go really higher. If you want you will need to move to Berlin or London I think