This code updates a WooCommerce product's price (including sale price) with data from its Comparison Set when the Comparison Set is created or its cached updated. [datafeedr][dfrcs]

add-comparison-set-price-to-product.php

<?php

/**
 * This code changes a WooCommerce product's price (including sale price) with data
 * from its Comparison Set when the Comparison Set is created or its cache is updated and
 * the Comparison Set has a highest and lowest price.
 *
 * This code modifies all of a WooCommerce Product's pricing fields.
 *
 * @param Dfrcs $compset
 */
function mycode_add_high_low_price_to_woocommerce_product_data( Dfrcs $compset ) {

	$product_id = isset( $compset->args['post_id'] ) ? $compset->args['post_id'] : 0;

	$product = wc_get_product( $product_id );

	if ( ! $product ) {
		return;
	}

	$main_active_price     = $product->get_price();
	$compset_highest_price = dfrcs_get_highest_priced_product_field( $compset, 'price' );
	$compset_lowest_price  = dfrcs_get_lowest_priced_product_field( $compset, 'finalprice' );

	/**
	 * If neither the highest price or the lowest price is found, return.
	 */
	if ( ! $compset_highest_price || ! $compset_lowest_price ) {
		return;
	}

	/**
	 * Convert the Comparison Set prices to floats so we can compare them
	 * to the main product's prices.
	 */
	$compset_highest_price = floatval( $compset_highest_price / 100 );
	$compset_lowest_price  = floatval( $compset_lowest_price / 100 );

	/**
	 * If the active price of the main product is less than or equal to the
	 * lowest price found in the Comparison Set, do nothing. No need to update the
	 * price for the main product as its price is already the best (or at least
	 * equal to the best price found in the Comparison Set).
	 *
	 * NOTE:
	 * 
	 * The problem with this is, once you modify the main product's price to a lower price
	 * if a future Comparison Set never has a lower price, the main product's price will
	 * only get updated to a correct higher price when the product is updated via a
	 * Product Set update.
	 *
	 * Remove this conditional if you always want the main product's price to be
	 * generated from the Comparison Set's low and high prices.
	 */
	if ( $main_active_price <= $compset_lowest_price ) {
		return;
	}

	/**
	 * If we made it this far, we need to update the prices of the main
	 * WooCommerce product.
	 */
	if ( $compset_lowest_price < $compset_highest_price ) {
		update_post_meta( $product->get_id(), '_regular_price', (float) $compset_highest_price );
		update_post_meta( $product->get_id(), '_sale_price', (float) $compset_lowest_price );
		update_post_meta( $product->get_id(), '_price', (float) $compset_lowest_price );
	} else {
		update_post_meta( $product->get_id(), '_regular_price', (float) $compset_highest_price );
		update_post_meta( $product->get_id(), '_sale_price', '' );
		update_post_meta( $product->get_id(), '_price', (float) $compset_lowest_price );
	}
}

add_action( 'dfrcs_compset_creation_complete', 'mycode_add_high_low_price_to_woocommerce_product_data', 20 );