Example of how to use pmpro_get_price_parts filter alongside PMPro Donations with custom "extras" included in price.

my_custom_get_price_parts.php

<?php

// Copy from below here...

/**
 * Example of how to use pmpro_get_price_parts filter alongside PMPro Donations
 * with custom "extras" included in price.
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_custom_get_price_parts( $price_parts, $invoice ) {
	if ( ! function_exists( 'pmprodon_get_price_components' ) ) {
		// PMPro donations not installed.
		return;
	}
	$donation_price_components = pmprodon_get_price_components( $invoice );

	$add_on_1_amount           = floatval(1); // Get dynamically from order.
	$add_on_2_amount           = floatval(2); // Get dynamically from order.
	$subtotal                  = $invoice->total - $add_on_1_amount - $add_on_2_amount;
	$donation_amount           = floatval( $donation_price_components['donation'] );
	$membership_amount         = $subtotal - $donation_amount;

	$price_parts[ 'subtotal' ] = array(
		'label' => 'Subtotal',
		'value' => pmpro_escape_price( pmpro_formatPrice( $subtotal ) ),
	);
	$price_parts[ 'sub_element_membership' ] = array(
		'label' => 'Membership Price',
		'value' => pmpro_escape_price( pmpro_formatPrice( $membership_amount ) ),
	);
	$price_parts[ 'sub_element_donation' ] = array(
		'label' => 'Donation',
		'value' => pmpro_escape_price( pmpro_formatPrice( $donation_amount ) ),
	);
	$price_parts[ 'add_on_1' ] = array(
		'label' => 'Add On 2',
		'value' => pmpro_escape_price( pmpro_formatPrice( $add_on_1_amount ) ),
	);
	$price_parts[ 'add_on_2' ] = array(
		'label' => 'Add On 1',
		'value' => pmpro_escape_price( pmpro_formatPrice( $add_on_2_amount ) ),
	);
	return $price_parts;
}
add_filter( 'pmpro_get_price_parts', 'my_custom_get_price_parts', 10, 2 );

function my_custom_price_part_element_class( $class, $element ) {
	if ( substr( $element, 0, 28 ) === "pmpro_price_part-sub_element" ) {
		$class[]= 'pmpro_price_part_sub';
	}
	return $class;
}
add_filter( 'pmpro_element_class', 'my_custom_price_part_element_class', 10, 2 );

This adds the donation amount and membership amount only to the invoice and email invoice: https://gist.github.com/MaryOJob/87f5a7a4988647691d7d92f75fa7fe8e