require_once MAGENTO . '/app/Mage.php';
    Mage::app();

$sku = '123';
$newPrice = '1.64';

updateProductPrices ( $sku, $newPrice );

function updateProductPrices ($sku, $newPrice) {
    Mage::app()->setCurrentStore(Mage_Core_Model_App::ADMIN_STORE_ID);

    $websites = Mage::app()->getWebsites();

    $product = Mage::getModel('catalog/product');
    $productId = $product->getIdBySku($sku);

    foreach ($websites as $_eachWebsite) {
        $_websiteId = $_eachWebsite->getWebsiteId();

        $websiteObj = new Mage_Core_Model_Website();
        $websiteObj->load($_websiteId);

        $storeIds = $websiteObj->getStoreIds();

        if (count($storeIds)) {
            foreach ($storeIds as $_eachStoreId) {
                $product->setStoreId($_eachStoreId)
                        ->load($productId);

                $oldPrice = $product->getPrice();



                if ($oldPrice != $newPrice) {
                    $product->setPrice($newPrice);
                    $product->save();

                    $product->setStoreId($_eachStoreId) -> setPrice($newPrice) ->save() ;

echo "<br/>Store ID: " . $_eachStoreId;
echo "<br/>Alt: " . $oldPrice;
echo "<br/>Neu: " . $newPrice;
                }
            }
        }

        unset($storeIds, $websiteObj, $_websiteId);
    }

    unset($product);
}