I had to pay the fee because the material value exceeded the limit for customs-free goods - which is around 80 Euros if I remember clearly. Above that, the more your items are worth, the bigger the sum you have to pay at customs.
The shipment fee I also had to pay wasn't fixed, but didn't vary as much.
I would have been happy, if I had known the rules at customs, because then, I could have let amazon send me two packages, or I would have simply ordered less items (or more for the two shipments )
Anyway, I got my goods, and that is what counts in the end