They have different pricing depending on the type of storage medium (Phone/USB Drive/Regular HDD)

https://www.copiefrance.fr/images/documents/tarifs_FR_2019_0...

Looking into it, it seems to not be considered a tax as it's not collected by the government, it also states that if you are importing a drive from a country that also collects such a "tax" you should seek to be reimbursed from the exporting country and pay the "tax" to the importing country.

Their FAQ: https://www.copiefrance.fr/fr/ressources/questions-reponses