/catalog/controller/product/category.php
Найти:
$special = $this->currency->format($this->tax->calculate($result['special'], $result['tax_class_id'], $this->config->get('config_tax')), $this->session->data['currency']);
Добавить после:
$discount_amount = $this->currency->format($this->tax->calculate(($result['price'] - $result['special']), $result['tax_class_id'], $this->config->get('config_tax')), $this->session->data['currency']);
Найти:
'price' => $price,
'special' => $special,
Добавить после:
'discount_amount' => $discount_amount,
/catalog/view/theme/default/template/product/category.tpl
Найти:
<span class="price-new"><?php echo $product['special']; ?></span> <span class="price-old"><?php echo $product['price']; ?></span>
Добавить после:
<span class="discount_amount"><?php echo 'Вы экономите '.$product['discount_amount']; ?></span>