We can think about this in a more nuanced way. The language of instruction, for example, is an important consideration. If foreign students are going to pursue degrees in France, in programs where the coursework is exclusively or primarily in French, then why not offer them the normal tuition-free deal? It would benefit French culture and France’s economy, while also respecting the fact that most of the students in question would come from former colonies.
English-language degree programs (thinking of other European countries) are a different story. There you end up with a situation that is more parasitic or exploitative.
How much would these students be willing to pay? How much does it cost the university to provide the tuition?
I'm in the UK. Universities charge £10k+ a year to foreign students (US, Australia, etc do the same) and they have queues of them waiting to sign up. There are plenty of foreign students willing to pay thousands of euros a year and it is madness for France to subsidise them, then complain that universities lack resources.
Nothing prevents some of the money from being used to provide scholarships to bright foreign students who couldn't otherwise afford it.
This needs to be looked at with pragmatism. The position that tuition has to be free is ideological, not pragmatical.
English-language degree programs (thinking of other European countries) are a different story. There you end up with a situation that is more parasitic or exploitative.