SO fiddle

Test Fiddle mainly for SO Questions

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<form id="myForm">
    <input name="price_500_365" value="12" />
    <input name="price_520_365" value="2" />
    <input name="price_530_365" value="32" />
</form>

JavaScript

var form = document.getElementById("myForm"), sum = 0;
for(var i=0; i<form.elements.length; i++) {
   var e = form.elements[i];
   if(e.type === 'text' && /price/.test(e.name)) sum += parseFloat(e.value);
}
alert(sum);