Add a select field that will change price in Woocommerce simple products

<?php
  // Frontend: custom select field in product single pages
add_action( 'woocommerce_before_add_to_cart_button', 'cxc_fabric_length_product_field' );

function cxc_fabric_length_product_field() {
	global $product;

	if( $product->is_type('variable') ) {
    	return; // Not variable products
    }  

    $domain = 'woocommerce';
    $text   = array(
    	__('cards', $domain),
    	__('card', $domain),
    	__('Total', $domain),
    	get_woocommerce_currency_symbol(),
    );

    // Select Options array
    $options = array(
    	""          => __('Select package'),
    	"12.00" => "1000 {$text[0]} - {$text[3]}0.012/{$text[1]} - {$text[2]} {$text[3]}12.00",
    	"15.00" => "2000 {$text[0]} - {$text[3]}0.008/{$text[1]} - {$text[2]} {$text[3]}15.00",
    	"20.00" => "3000 {$text[0]} - {$text[3]}0.007/{$text[1]} - {$text[2]} {$text[3]}20.00",
    	"25.00" => "4000 {$text[0]} - {$text[3]}0.006/{$text[1]} - {$text[2]} {$text[3]}25.00",
    );

    // Select field
    woocommerce_form_field( 'cards_pack', array(
    	'type'          => 'select',
    	'class'         => array('my-field-class form-row-wide'),
    	'label'         => __('Cards Pack selection', $domain),
    	'required'      => true,
    	'options'       => $options,
    ), '' );

    // Data to be transmitted to jQuery
    $base_price = (float) wc_get_price_to_display( $product );
    $prices = array(
    	''      => wc_price($base_price),
    	'12.00' => wc_price($base_price + 12),
    	'15.00' => wc_price($base_price + 15),
    	'20.00' => wc_price($base_price + 20),
    	'25.00' => wc_price($base_price + 25),
    )
    // jQuery code
    ?>
    <script>
    	jQuery(function($){
    		var a = <?php echo json_encode($prices); ?>,
    		b = 'p.price',
    		c = 'select[name="cards_pack"]';

    		$(c).on( 'change', function(){
    			$.each( a, function( key, value ){
    				if( $(c).val() == key )
    					$(b).html(value);
    			});
    		});
    	});
    </script>
    <?php
}
?>

<?php
// Add selected pack data as custom data to cart items
add_filter( 'woocommerce_add_cart_item_data', 'cxc_add_pack_data_to_cart_item_data', 20, 2 );

function cxc_add_pack_data_to_cart_item_data( $cart_item_data, $product_id ){
	if( ! isset($_POST['cards_pack']) ){
		return $cart_item_data;
	}

	$pack_price = (float) sanitize_text_field( $_POST['cards_pack'] );
	if( empty($pack_price) ){
		return $cart_item_data;
	}

	if( $pack_price == 12.00 ) {
		$cards = 1000;
	} elseif($pack_price == 15.00) {
		$cards = 2000;
	} elseif($pack_price == 20.00) { 
		$cards = 3000;
	} elseif($pack_price == 25.00) {
		$cards = 4000;	
	} 

    $product    = wc_get_product($product_id); // The WC_Product Object
    $base_price = (float) $product->get_price();

    // New price calculation
    $new_price = $base_price + $pack_price;

    // Prepare and save the data array
    $cart_item_data['pack_data'] = array(
    	'cards'     => (int)   $cards,
    	'pack'      => (int)   $pack_price,
    	'new_price' => (float) $new_price,
    );
    $cart_item_data['unique_key'] = md5( microtime() . rand() ); // Make each item unique

    return $cart_item_data;
}

// Set conditionally a custom item price
add_action( 'woocommerce_before_calculate_totals', 'cxc_set_cutom_cart_item_price', 20, 1 );

function cxc_set_cutom_cart_item_price( $cart ) {
	if ( is_admin() && ! defined( 'DOING_AJAX' ) ){
		return;
	}

	if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 ){
		return;
	}

	foreach (  $cart->get_cart() as $cart_item ) {
		if ( isset( $cart_item['pack_data']['new_price'] ) ){
			$cart_item['data']->set_price( $cart_item['pack_data']['new_price'] );
		}
	}
}
?>

<?php
// Display custom data in  checkout page
add_filter( 'woocommerce_get_item_data', 'cxc_display_custom_cart_item_data', 10, 2 );

function cxc_display_custom_cart_item_data( $cart_data, $cart_item ) {
	$domain = 'woocommerce';

	if ( isset( $cart_item['pack_data']['new_price'] ) ){
		$cart_data[] = array('name' => __( 'Cards pack', $domain ),
			'value' => $cart_item['pack_data']['cards'] );
	}
	return $cart_data;
}
?>