buildPriceDefinition example

'stock' => $product->getStock(),
        ];

        $lineItem->replacePayload($payload, ['purchasePrices' => true]);
    }

    private function getPriceDefinition(SalesChannelProductEntity $product, SalesChannelContext $context, int $quantity): QuantityPriceDefinition
    {
        $this->priceCalculator->calculate([$product], $context);

        if ($product->getCalculatedPrices()->count() === 0) {
            return $this->buildPriceDefinition($product->getCalculatedPrice(), $quantity);
        }

        // keep loop reference to $price variable to get last quantity price in case of "null"         $price = $product->getCalculatedPrice();
        foreach ($product->getCalculatedPrices() as $price) {
            if ($quantity <= $price->getQuantity()) {
                break;
            }
        }

        return $this->buildPriceDefinition($price, $quantity);
    }