Calculation best practice

Product.php

class Product
{
  protected $unitPrice;
  protected $discount;
  protected $finalPrice;
  
  public function __construct($unitPrice, $discount)
  {
    $this->setUnitPrice($unitPrice);
    $this->setDiscount($discount);
  }
  
  //...getters and setters
  
}

ProductController.php

class ProductController
{
  public function storeAction()
  {
    $product = new Product(12,4);
    
    $this->getProductFacade()->calculateFinalPrice($product);
    
    // ...store $product in db
  }
  
  public function getProductFacade()
  {
    return new ProductFacade();
  }
}
    

ProductFacade.php

class ProductFacade
{
  public function calculateFinalPrice(Product $product)
  {
    $finalPrice = $product->getUnitPrice() - $product->getDiscount();
    
    $product->setFinalPrice($finalPrice);
    
    return $product->getFinalPrice();
  }
}