What is important to me is the level of service, not really the fee.
For Instance the UK CAA has a rather poor level of service according to my experience (they made a mistake at my expense each of the three last time I had to deal with them, the online service is incredibly archaïc)
In France, you have an on line access to your entire dossier, they answer reasonably quickly etc.
On the other hand, France likes demanding thing ultra vires. They refuse ELP's issued abroad, they demand that you train for GNSS approaches at an ATO otherwise they say you're not allowed to fly one, and maybe other things.
I would be interesting to get a review that would compare things in details.