Calculation of Product Sales Statistics

[storyboo]

I figure it would be handy to have a query that would show me the number of times a product had sold in the store and ALSO the profit it resulted in. This code below works however...the prices arent right. Everything is the quantity X $3.49....but not all of my products are 3.49..some are 17.00 etc. Why is it doing this?

<?php
$rowsPerPage = 500;

if(isset($_GET['page'])){
	$page = $_GET['page'];
} else {
	$page = 0;
}

$query = "SELECT sum(a.quantity) AS quan, a.productId, b.name FROM `".$glob['dbprefix']."CubeCart_order_inv` a INNER JOIN `".$glob['dbprefix']."CubeCart_inventory` b ON a.productId = b.productId GROUP BY productId DESC ORDER BY `quan` DESC";

$results = $db->select($query, $rowsPerPage, $page);
$noResults = $db->numrows($query);
$totalItemsSold = $db->select("SELECT SUM(quantity) as totalProducts FROM  `".$glob['dbprefix']."CubeCart_order_inv`");
$prodprice = $db->select("SELECT (`price`) as prodprice FROM  `".$glob['dbprefix']."CubeCart_inventory`");

if($results==TRUE) {
  	$i=0;
	$chartData = array();

$keyStr = "<table width='100%' border='0' cellspacing='1' cellpadding='3' class='mainTable'>
<tr>
	<td class='tdTitle' style='text-align: center;'>Rank</td>
	<td class='tdTitle'>Product Name</td>
	<td class='tdTitle' style='text-align: center;'>No of Sales</td>
	<td class='tdTitle' style='text-align: center;'>Percentage of Sales</td>
</tr>\n";

for ($i=0; $i<$noResults; $i++){

	$cellColor = cellColor($i);	

	$percentage = ($results[$i]['quan'] * $prodprice[0]['prodprice']);
	$percentage = number_format($percentage, 2);
	if ($percentage >= 0 && $results[$i]['quan'] >= 1) {
		$position = (($page*$rowsPerPage)+1)+$i;
		$chartData[] = array($position,$percentage);

		$keyStr .= "<tr>
			<td class='copyText' style='text-align: center;'>".$position."</td>
			<td class='copyText'>".$results[$i]['name']."</td>
			<td class='copyText' style='text-align: center;'>".$results[$i]['quan']."</td>
			<td class='copyText' style='text-align: center;'>$".$percentage."</td>
		</tr>\n";
	}
}

$keyStr .= "</table>";

?>
<?php
echo $keyStr;

} else { 
	echo "<p class='copyText'>No Products have sold in your store.</p>";
} 
?>

[Krik]

$percentage = ($results[$i]['quan'] * $prodprice[0]['prodprice']);

I am guessing the first returned items price is 3.49? As such that "0" needs to be a variable that represents result row you need the price from.