Step 1) Create di.xml

<?xml version="1.0"?>
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">

	<type name="MagentoCheckoutModelDefaultConfigProvider">
	    <plugin name="AddAttPlug" type="[vendor][module]ModelPluginDefaultConfigProvider" />
	</type>
</config>

Step 2) create plugin file DefaultConfigProvider.php

class DefaultConfigProvider 
{

  /**
    *@var checkoutSession
    */
    protected $checkoutSession;

    /**
    *Constructor
    * @param CheckoutSession $checkoutSession
    */
    public function __construct(CheckoutSession $checkoutSession)
    {
        $this->checkoutSession = $checkoutSession;
    }
    public function afterGetConfig(MagentoCheckoutModelDefaultConfigProvider $subject, $config)
    {
    	$objectManager = MagentoFrameworkAppObjectManager::getInstance(); 
        foreach ($config['quoteItemData'] as &$item) {
            $priceHelper = $objectManager->create('MagentoFrameworkPricingHelperData');
            $quoteItem = $this->checkoutSession->getQuote()->getItemById($item['item_id']);
            $price =  $quoteItem->getProduct()->getPrice();
            $formattedPrice = $priceHelper->currency($price, true, false);
            $item['originalprice'] = $formattedPrice;
        }
       return $config;
    }
}

Step 3) Override the /vendor/magento/module-checkout/view/frontend/web/js/view/summary/item/details.js to your module

**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

define([
    'uiComponent',
    'Magento_Checkout/js/model/quote'
], function (Component) {
    'use strict';

    return Component.extend({
        defaults: {
            template: 'Magento_Checkout/summary/item/details'
        },

        /**
         * @param {Object} quoteItem
         * @return {String}
         */
        getValue: function (quoteItem) {
            return quoteItem.name;
        },
        getItemBaseprice: function (quoteItem) {
                return this.getPropertyDataFromItem(quoteItem, 'originalprice');
        },
        getPropertyDataFromItem: function (quoteItem, propertyName) {
                var property,
                    itemDetails;
                if (quoteItem.hasOwnProperty(propertyName)) {
                    property = quoteItem[propertyName];
                }
                var quoteItem = this.getItemFromQuote(quoteItem);
                if (quoteItem.hasOwnProperty(propertyName)) {
                    property = quoteItem[propertyName];
                }
                if (property) {
                    this.storage().set('item_details' + quoteItem.item_id + propertyName, property);
                    return property;
                }
                itemDetails = this.storage().get('item_details' + quoteItem.item_id + propertyName);
                return itemDetails ? itemDetails : false;
            },
            getItemFromQuote: function (item) {
                var items = quote.getItems();
                var quoteItems = items.filter(function (quoteItem) {
                    return quoteItem.item_id == item.item_id;
                });
                if (quoteItems.length == 0) {
                    return false;
                }
                return quoteItems[0];
            }
    });
});

Step 4) Override the vendor/magento/module-checkout/view/frontend/web/template/summary/item/details.html to your module add the below line.

<span class="originalprice" data-bind="text: getItemBaseprice($parent)"></span>