Custom Field string only shows price including tax

[V1llum]

Hi,
I have a danish webshop meaning that there is a 25% tax on everything. I prefer to show all my prices excluding taxes though. On one of my products i have made a cusom field string, allowing people to buy more than one licens. The custom field string creates a dropdown menu, but this menu always shows the prices including taxes. The rest of my webshop shows all prices excluding taxes. How do i change this?
Link: http://new.se-lyden.dk/index.php/component/virtuemart/total-pakken-detail

The prices are supposed to be:
1 klasse: +250 kr
2 klasser: +500 kr
3 klasser: +750 kr and so on.
But all of the prices are shown with an additional 25% tax.

Thank you for your help.

[Studio 42]

If you have updated to VM3.0.x
in the http://yourshop.com/administrator/index.php?option=com_virtuemart&view=config
In the price tab, you can disable variant taxes for all your shop