Create API Interface to get price by product id

Api/ProductRepositoryInterface.php

+<?php
+
+namespace Plugilo\Plugilo\Api;
+
+interface ProductRepositoryInterface
+{
+    /**
+     * Return a filtered product.
+     *
+     * @param int $id
+     * @return \Plugilo\Plugilo\Api\ResponseItemInterface
+     * @throws \Magento\Framework\Exception\NoSuchEntityException
+     */
+    public function getItem(int $id);
+}

Api/ResponseItemInterface.php

+<?php
+
+namespace Plugilo\Plugilo\Api;
+
+interface ResponseItemInterface
+{
+    const DATA_ID = 'id';
+    const DATA_PRICE = 'price';
+
+    /**
+     * @return int
+     */
+    public function getId();
+    /**
+     * @return float
+     */
+    public function getPrice();
+
+    /**
+     * @param int $id
+     * @return $this
+     */
+    public function setId(int $id);
+
+    /**
+     * @param float $price
+     * @return $this
+     */
+    public function setPrice(float $price);
+}

Model/Api/ProductRepository.php

+<?php
+
+namespace Plugilo\Plugilo\Model\Api;
+
+use Plugilo\Plugilo\Api\ProductRepositoryInterface;
+use Plugilo\Plugilo\Api\ResponseItemInterfaceFactory;
+use Magento\Catalog\Api\Data\ProductInterface;
+use Magento\Catalog\Model\ResourceModel\Product\CollectionFactory;
+use Magento\Framework\Exception\NoSuchEntityException;
+
+/**
+ * Class ProductRepository
+ */
+class ProductRepository implements ProductRepositoryInterface
+{
+    /**
+     * @var CollectionFactory
+     */
+    private $productCollectionFactory;
+
+    /**
+     * @var ResponseItemInterfaceFactory
+     */
+    private $responseItemFactory;
+
+    /**
+     * @param CollectionFactory $productCollectionFactory
+     * @param ResponseItemInterfaceFactory $responseItemFactory
+     */
+    public function __construct(
+        CollectionFactory $productCollectionFactory,
+        ResponseItemInterfaceFactory $responseItemFactory
+    ) {
+        $this->productCollectionFactory = $productCollectionFactory;
+        $this->responseItemFactory = $responseItemFactory;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @param int $id
+     * @return ResponseItemInterface
+     * @throws NoSuchEntityException
+     */
+    public function getItem(int $id): mixed
+    {
+        $collection = $this->getProductCollection()
+            ->addAttributeToFilter('entity_id', ['eq' => $id]);
+        /** @var ProductInterface $product */
+        $product = $collection->getFirstItem();
+        if (!$product->getId()) {
+            throw new NoSuchEntityException(__('Product not found'));
+        }
+        return $this->getResponseItemFromProduct($product);
+    }
+
+    /**
+     * @return Collection
+     */
+    private function getProductCollection(): mixed
+    {
+        /** @var Collection $collection */
+        $collection = $this->productCollectionFactory->create();
+        $collection
+            ->addAttributeToSelect(
+                [
+                    'entity_id',
+                    ProductInterface::PRICE,
+                ]
+            );
+        return $collection;
+    }
+    /**
+     * @param ProductInterface $product
+     * @return ResponseItemInterface
+     */
+    private function getResponseItemFromProduct(ProductInterface $product): mixed
+    {
+        /** @var ResponseItemInterface $responseItem */
+        $responseItem = $this->responseItemFactory->create();
+        $responseItem->setId($product->getId())->setPrice($product->getPrice());
+        return $responseItem;
+    }
+}

Model/Api/ResponseItem.php

+<?php
+
+namespace Plugilo\Plugilo\Model\Api;
+
+use Plugilo\Plugilo\Api\ResponseItemInterface;
+use Magento\Framework\DataObject;
+use Symfony\Component\Config\Definition\FloatNode;
+
+/**
+ * Class ResponseItem
+ */
+class ResponseItem extends DataObject implements ResponseItemInterface
+{
+    public function getId(): int
+    {
+        return $this->_getData(self::DATA_ID);
+    }
+    public function getPrice(): float
+    {
+        return $this->_getData(self::DATA_PRICE);
+    }
+
+    /**
+     * @param int $id
+     * @return $this
+     */
+    public function setId(int $id): mixed
+    {
+        return $this->setData(self::DATA_ID, $id);
+    }
+
+    /**
+     * @param float $price
+     * @return $this
+     */
+    public function setPrice(float $price): mixed
+    {
+        return $this->setData(self::DATA_PRICE, $price);
+    }
+}

etc/di.xml

+<?xml version="1.0" ?>
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
+    <preference for="Plugilo\Plugilo\Api\ProductRepositoryInterface" type="Plugilo\Plugilo\Model\Api\ProductRepository"/>
+    <preference for="Plugilo\Plugilo\Api\ResponseItemInterface" type="Plugilo\Plugilo\Model\Api\ResponseItem"/>
+</config>

etc/webapi.xml

+<?xml version="1.0"?>
+<routes xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Webapi:etc/webapi.xsd">
+    <route url="/V1/plugilo/getProduct/:id" method="GET">
+        <service class="Plugilo\Plugilo\Api\ProductRepositoryInterface" method="getItem" />
+        <resources>
+            <resource ref="anonymous" />
+        </resources>
+    </route>
+</routes>