In Europe Ammo is a lot more expensive than in the us and fewer people are reloading.
For instance, a Hornady 300 win whitetail is $40 in the us and in europe it is 60€/$70 !!
And European ammo manufacturer are even more expensive (RWS, NORMA, LAPUA, etc.)
The Ukranian war also driving shortage and price increase in Europe (looks like components were used primary for the defense industry)
Sologne prices are very high, that's a small company they most likely do not have the volume to lower their price - they position themselves. as alternative to big manufacturer with specific bullets and not common calibers.
I was lucky to buy a few boxes of 458 lott from cartouche SOlogne at my local gunstore - few african hunters, ammo on the shelf for very long time, got a crazy good deal.