Example how to handle "packed" meta values in WooCommerce's new product editor

example-complex-product-meta-fields.php

<?php

use Automattic\WooCommerce\Admin\Features\ProductBlockEditor\ProductTemplates\GroupInterface;

add_filter(
	'woocommerce_rest_prepare_product_object',
	function ( $response, $post ) {
		$custom_regular_prices_encoded = get_post_meta( $post->get_id(), '_custom_regular_prices', true );

		$custom_regular_prices = json_decode(
			'' === $custom_regular_prices_encoded ? '{}' : $custom_regular_prices_encoded,
			true,
		);

		$response->data['custom_regular_price_1'] = isset( $custom_regular_prices['price_1'] ) ? $custom_regular_prices['price_1'] : '';
		$response->data['custom_regular_price_2'] = isset( $custom_regular_prices['price_2'] ) ? $custom_regular_prices['price_2'] : '';

		return $response;
	},
	10,
	2,
);

add_filter(
	'woocommerce_rest_insert_product_object',
	function ( $product, $request ) {
		$product_id = $product->get_id();
		$params     = $request->get_params();

		$existing_custom_regular_prices_encoded = get_post_meta( $product_id, '_custom_regular_prices', true );

		$existing_custom_regular_prices = json_decode(
			'' === $existing_custom_regular_prices_encoded ? '{}' : $existing_custom_regular_prices_encoded,
			true,
		);

		$existing_price_1 = isset( $existing_custom_regular_prices['price_1'] ) ? $existing_custom_regular_prices['price_1'] : '';
		$existing_price_2 = isset( $existing_custom_regular_prices['price_2'] ) ? $existing_custom_regular_prices['price_2'] : '';

		$custom_regular_prices = [
			'price_1' => isset( $params['custom_regular_price_1'] ) ? $params['custom_regular_price_1'] : $existing_price_1,
			'price_2' => isset( $params['custom_regular_price_2'] ) ? $params['custom_regular_price_2'] : $existing_price_2,
		];

		update_post_meta( $product_id, '_custom_regular_prices', wp_json_encode( $custom_regular_prices ) );
	},
	10,
	2,
);

add_action(
	'rest_api_init',
	function () {
		add_action(
			'woocommerce_block_template_area_product-form_after_add_block_pricing',
			function ( GroupInterface $pricing_group ) {

				$section = $pricing_group->add_section(
					array(
						'id'         => 'example-complex-product-meta-fields-pricing-section',
						'attributes' => array(
							'title' => __( 'My Custom Pricing Fields', 'YOUR_TEXT_DOMAIN' ),
						),
					)
				);

				$section->add_block(
					array(
						'id'         => 'example-complex-product-meta-fields-custom-regular-price-1',
						'blockName'  => 'woocommerce/product-pricing-field',
						'attributes' => array(
							'label'    => __( 'Custom Regular Price 1', 'YOUR_TEXT_DOMAIN' ),
							'property' => 'custom_regular_price_1',
						),
					)
				);

				$section->add_block(
					array(
						'id'         => 'example-complex-product-meta-fields-custom-regular-price-2',
						'blockName'  => 'woocommerce/product-pricing-field',
						'attributes' => array(
							'label'    => __( 'Custom Regular Price 2', 'YOUR_TEXT_DOMAIN' ),
							'property' => 'custom_regular_price_2',
						),
					)
				);
			}
		);

	},
	9,
	0
);