Вставь в функции:
add_filter('woocommerce_available_variation', function ($value, $object = null, $variation = null) {
if ($value['price_html'] == '') {
$value['price_html'] = '<span class="price">' . $variation->get_price_html() . '</span>';
}
return $value;
}, 10, 3);
или:
add_filter( 'woocommerce_show_variation_price', 'filter_show_variation_price', 10, 3 );
function filter_show_variation_price( $condition, $product, $variation ){
if( $variation->get_price() === "" ) return false;
else return true;
}