Add costs to a WooCommerce shipping rate in a pattern

functions.php

function wc_ninja_change_shipping_rate_cost( $rates, $package ) {
	$shipping_method_id = 'table_rate:14:1';
	$cost_per_case = 50;
	$products_per_case = 12;

	// Make sure the specific table rate is available
	if ( isset( $rates[$shipping_method_id] ) ) {
		$products_in_cart = WC()->cart->cart_contents_count;
		$additional_cost = 0;

		if ( $products_in_cart > $products_per_case ) {
			// Calculate costs of extra cases
			$extra_cases_in_cart = floor( ($products_in_cart - $products_per_case) / $products_per_case );
			if ( $extra_cases_in_cart ) {
				(int)$additional_cost = ($extra_cases_in_cart * $cost_per_case) + $additional_cost;
			}

			// Calculate the remaining single bottle prices
			$single_bottles_left = $products_in_cart % $products_per_case;
			if ( $single_bottles_left ) {
				(int)$additional_cost = (wc_ninja_single_bottle_costs( $single_bottles_left )) + $additional_cost;
			}

			// Add our additional cost to the shipping method
			if ( $additional_cost ) {
				$rates[$shipping_method_id]->cost = $rates[$shipping_method_id]->cost + $additional_cost;
			}
		}
	}

	return $rates;
}

add_filter( 'woocommerce_package_rates', 'wc_ninja_change_shipping_rate_cost', 10, 2 );

function wc_ninja_single_bottle_costs( $number = 1 ) {
	switch ( $number ) {
		case 1:
			$cost = 22;
			break;

		case 2:
			$cost = 23;
			break;

		case 3:
		case 4:
			$cost = 25;
			break;

		default:
			$cost = 26;
			break;
	}

	return $cost;
}