[Only show cheapest shipping option] #woo

show-cheapest-option.php

/**
 * Only display the cheapest shipping rate
 */
function my_only_show_cheapest_shipping_rate( $rates, $package ) {

	$cheapest_method = '';

	// Loop through shipping rates
	if ( is_array( $rates ) ) :
		foreach ( $rates as $key => $rate ) :

			// Set variables when the rate is cheaper than the one saved
			if ( empty( $cheapest_method ) || $rate->cost < $cheapest_method->cost ) :
				$cheapest_method = $rate;
			endif;

		endforeach;
	endif;

	// Return the cheapest rate when possible
	if ( ! empty( $cheapest_method ) ) :
		return array( $cheapest_method->id => $cheapest_method );
	endif;

	return $rates;

}
add_action( 'woocommerce_package_rates', 'my_only_show_cheapest_shipping_rate', 10, 2 );

show-most-expensive-option.php

function my_only_show_most_expensive_shipping_rate( $rates, $package ) {

	$most_expensive_method = '';

	// Loop through shipping rates
	if ( is_array( $rates ) ) :
		foreach ( $rates as $key => $rate ) :

			// Set variables when the rate is more expensive than the one saved
			if ( empty( $most_expensive_method ) || $rate->cost > $most_expensive_method->cost ) :
				$most_expensive_method = $rate;
			endif;

		endforeach;
	endif;

	// Return the most expensive rate when possible
	if ( ! empty( $most_expensive_method ) ) :
		return array( $most_expensive_method->id => $most_expensive_method );
	endif;

	return $rates;

}
add_action( 'woocommerce_package_rates', 'my_only_show_most_expensive_shipping_rate', 10, 2 );