It's a similar situation here in the UK too, unfortunately.
I don't know what percentage mark-up there is, but I've noticed that whatever a set costs in Euros, the figure is almost the same here, but with a Pound symbol instead.
For example, Specials cost about £1.99 here, which is almost 3 Euros.
I suppose the extra cost is to cover the expense of distributing to other countries, but it seems a bit strange that prices in the Netherlands are so much higher, given that it's much closer to Germany than the UK.