There's other factors at play here, I don't think GMK charges any more or less for any of the vendors, but you have to factor in the cost of labor.
The vendors that run the GB's do a lot behind the scenes, and that requires labor. Someone who's in Germany will therefor charge a bit more than someone in say Singapore, where the labor prices are lower.
because VAT
hard to offer good prices if you have to factor in 19 to 25% of the item value in the final price
All of those are fair points, but from business perspective, it should not happen, that item produced literately next door, is more expensive locally, than the same exported item.
Every seller has to deal with additional costs, but GMK margins are high enough, from my point of view, so they can make sure, that regular price is equal or lower on local market, in comparison to foreign market.
What is the point of publishing pricing, which at the end might be 25% more...