Hi,
Are you sure the prices.php file only impacts the catalog (product list and product page) and does not change anything in the shopping cart?
For example, I need this following setting :
catalog price showed (product list and product page)
2 695,00$ (without TVA)
In the shopping cart
2 695,00$ (subtotal)
403.71 $ (TVA)
3 098.71 $ (TTC)
I upgrade a website from Joomla 2.x to 3.x and this setting works on VirtueMart v.1.1.3 and I can't do the same thing in VirtueMart v.3.4.2