Is 30k/year normal in France?

I'd say it's a graduate salary in a small to medium-size city for someone with a masters

Unfortunately....

I don’t know who might apply for this wage. No offense

You are right the starting wage is way below what shiny startups or software consultancies are able to offer, even in France. To be fully transparent, I started working with them as an experienced dev but rookie clojurist (with 10 days of XP) as I wanted to learn Clojure. Today I stay because the team is great, the working culture fits me very well, and I think the product has great potential (with most of the risk behind). In my ~6 years career, I have learned that a team fit is much harder to find than a big paycheck. These are all very personal choices, that suit my lifestyle and my values, and won't suit everyone.