it's because the number is being passed using the comma as a decimal separator, javascript does not recognize the comma as a decimal separator
try this function instead, it will convert the comma to a period:
<script type="text/javascript">
function getPrice(option, prodPrice) {
var prodPrice = prodPrice.replace(",",".");
var thePrice;
switch (option) {
case '10':
thePrice = parseFloat(prodPrice)-1;
break;
case '15':
thePrice = parseFloat(prodPrice);
break;
case '20':
thePrice = parseFloat(prodPrice)+2;
break;
case '25':
thePrice = parseFloat(prodPrice)+3;
break;
case '30':
thePrice = parseFloat(prodPrice)+4;
break;
case '35':
thePrice = parseFloat(prodPrice)+5;
break;
case '40':
thePrice = parseFloat(prodPrice)+6;
break;
case '45':
thePrice = parseFloat(prodPrice)+7;
break;
case '50':
thePrice = parseFloat(prodPrice)+8;
break;
case '55':
thePrice = parseFloat(prodPrice)+9;
break;
default:
thePrice = parseFloat(prodPrice)+10;
}
return thePrice;
}
</script>
also in the onchange event, there needs to be single quotes around the price that is being passed:
onchange="document.getElementById('cmPrice').innerHTML = getPrice(document.FrogStyling_1_ATC_<%=rsDetail.Fields("ProductID").value%>.FrogStyling_1_Size_Add[document.FrogStyling_1_ATC_<%=rsDetail.Fields("ProductID").value%>.FrogStyling_1_Size_Add.selectedIndex].value, '<%= FormatNumber((rsDetail.Fields.Item("ProductPrice").Value), 2, -2, -2, -2) %>')"