solved:
\administrator\components\com_virtuemart\helpers\currencydisplay.php
//This could be easily extended by product specific settings
if(!empty($this->_priceConfig[$name][0])){
if(!empty($price)){
$vis = "block";
$priceFormatted = $this->priceDisplay($price,0,(float)$quantity,false,$this->_priceConfig[$name][1]);
$temp = explode(",", $priceFormatted);
$tmp = explode(" ", $temp[1]);
$afterComa = '<span style="font-size:10px">'.$tmp[0]."</span><sup>".$tmp[1]."</sup>";
$priceFormatted = $temp[0].",".$afterComa;