Cmon man, its only a list box with a variable for each lol, ya know it makes sence :p
dont make me move dave down on my christmas list LOL 
PHP Code:
<form name="form1" method="post" action="echo.php">
<select name="select">
<option value="whatever price 1">50</option>
<option value="whatever price 2" selected>10</option>
</select>
<input type="submit" name="Submit" value="Submit">
</form>
<body>
<p>PHP var placed into the calculation <?=$select?></p>
</body>
^
May be terrably basic as i havnt used php for ageeeeees (CFM all the way now)
"Everybody loves a joker, But no one likes a fool"