Incorrect estimated fees per unit for EU

i have just checked the net payments i am receiving for some products. I am based in the UK, store my products in the UK, but sell to EU as well. All via FBA.

The estimated fee per unit sold in the UK market is very accurate, only out by a few pennies.

however, the estimated fees are way off for one item i’m selling in France and Germany. Selling the same item in the UK and the esimtate is fine. The Euro estimate is way off. The item is only circa 15 euro and the estimate is off by at least a couple of euro.

Is this normal? i expected inaccuracies however a couple of euro off on an item that only sells for around 15 euro.