مراد,
Возможный вариант...
<!DOCTYPE HTML>
<html>
<head>
<title></title>
<meta charset="utf-8" />
</head>
<body>
<select name="spisok" id="spisok">
<option value="1">600$</option>
<option value="1">800$</option>
<option value="1">9000$</option>
<option value="1">1000$</option>
<option value="1">привет</option>
</select>
<input name="cena" type="text" />
<script>
var select = document.getElementById('spisok');
select.addEventListener('change', function() {
var i = this.selectedIndex
var text = this.options[i].text;
document.getElementsByName('cena')[0].value=text
;
});
</script>
</body>
</html>