sorry for my late reply, I was on vacation.
According to my experience, some products return different values as it shows on the Amazon page.
Nevertheless I updated the calculation of the AmazonPrice placeholder in the meantime. It is being tested until it gets to the next official release. You can grab this file and replace it in your plugin root dir if you like to test it too: http://svn.wp-plugins.org/amazonsimpleadmin/trunk/AsaCore.php