<html>
<head>
</head>
<body>
<select id="s">
<option value="foo">foo</option>
<option value="bar">bar</option>
<option value="baz">baz</option>
</select>
<div id="out"></div>
<script>
display=function(val){
switch(val){
case "foo": return "$100"
case "bar": return "$200"
case "baz": return "$300"
}
}
s.onchange=function(){out.innerHTML=display(this.value)}
s.onchange() //set default
</script>
</body>
</html>