在篮子中设置自定义总行价格- Magento

我正在开发一个B2B网店在Magento。在向购物篮中添加产品时，它将调用外部API来根据用户、产品和数量查找折扣。问题是API只返回总折扣价格。

。加上10件5美元的商品，总折扣价可能是40美元。所以理想情况下，购物车应该显示$5 x 10 = $40。

我已经通过在我的模块config.xml中覆盖Mage_Sales_Model_Quote_Item实现了这一点:

<global>
    <models>
        <sales>
            <rewrite>
                <quote_item>Frigg_Import_Model_QuoteItem</quote_item>
            </rewrite>
        </sales>
    </models>
</global>

class Frigg_Import_Model_QuoteItem extends Mage_Sales_Model_Quote_Item
{
    protected $customRowTotalPrice = null;
    public function setCustomRowTotalPrice($price)
    {
        $this->customRowTotalPrice = $price;
    }
    public function calcRowTotal()
    {
        if ($this->customRowTotalPrice !== null) {
            $this->setRowTotal($this->getStore()->roundPrice($this->customRowTotalPrice));
            $this->setBaseRowTotal($this->getStore()->roundPrice($this->customRowTotalPrice));
            return $this;
        }
        $qty = $this->getTotalQty();
        $total = $this->getStore()->roundPrice($this->getCalculationPriceOriginal()) * $qty;
        $baseTotal = $this->getStore()->roundPrice($this->getBaseCalculationPriceOriginal()) * $qty;
        $this->setRowTotal($this->getStore()->roundPrice($total));
        $this->setBaseRowTotal($this->getStore()->roundPrice($baseTotal));
        return $this;
    }
}

然后处理事件checkout_cart_product_add_after并将其传递给我的观察者方法setPriceForItem:

<?php
class Frigg_Import_Model_Observer
{
    // Event: Price for single item
    public function setPriceForItem(Varien_Event_Observer $observer)
    {
        $customer = Mage::getSingleton('customer/session')->getCustomer();
        $item = $observer->getQuoteItem();
        if ($item->getParentItem()) {
            $item = $item->getParentItem();
        }
        $quantity = $item->getQty(); // e.g. 5
        $product = $item->getProduct();
        // Call API here and get the total price based on quantity (e.g. 40)
        // ....
        $customTotalRowPriceFromAPI = 40;
        if ($customTotalRowPriceFromAPI) {
            $item->setCustomRowTotalPrice($customTotalRowPriceFromAPI);
            $item->getProduct()->setIsSuperMode(true);
            $item->save();
        }
    }
}

现在可以工作了，但只在添加到篮子时。当我重新加载浏览器或转到购物车页面时，行价格已重置为原始价格(在本例中为$5 x 10 = $50)。

有人发现我的错误吗?我希望我已经解释清楚了