Display price in variation option dropdown for products that have only one attribute.

display_price_in_variation_options.php

<?php
/**
 * Display price in variation options dropdown for products that have only one attribute.
 *
 * @author Travis Aaron Wagner <[email protected]>
 * @param  string $term Existing option term value.
 * @return string $term Existing option term value or updated term value with price.
 */
function display_price_in_variation_options( $term ) {
	$product = wc_get_product();
	$id      = $product->get_id();
	if ( empty( $term ) || empty( $id ) ) {
		return $term;
	}
	if ( $product->is_type( 'variable' ) ) {
		$product_variations = $product->get_available_variations();
	} else {
		return $term;
	}
	foreach ( $product_variations as $variation ) {
		if ( count( $variation['attributes'] ) > 1 ) {
			return $term;
		}
		$attribute = array_values( $variation['attributes'] )[0];
		if ( $attribute === $term ) {
			$term .= ' (' . wp_strip_all_tags( wc_price( $variation['display_price'] ) ) . ')';
		}
	}
	return $term;
}
add_filter( 'woocommerce_variation_option_name', 'display_price_in_variation_options' );