PHP is the way to go here, for sure. You can have a template file for your page, and include a keyword package PHP file for each page. Simple, easy, and flexible.
Example keyword file:
Code:
$product_name='Widget'
$product_image='image.jpg'
$product_merchant_link='http://mymerchantlink.com'
Then a template that includes this file.
HTML Code:
<title>Welcome to the <?php echo $product_name; ?> page!</title>
<body>
<img href=\"<?php echo $product_image; ?>\">
<p>Buy <?php echo $product_name; ?> from <a href=\"<?php echo $product_merchant_link\"; ?> here!</a></p>
Pretty basic, but useful.