Adjust price based on the total number of files/uploads

add_filter('woocommerce_add_cart_item_data', 'custom_codedropz_change_price', 100, 2 );
add_filter('woocommerce_before_calculate_totals','set_codedropz_calculate_price', 20, 1 );

function custom_codedropz_change_price( $cart_item_data, $product_id ){

    // Bail early
    if( ! isset( $cart_item_data['dnd-wc-file-upload'] ) ){
        return $cart_item_data;
    }

    // Get total no. of files
    $total_files = count( $cart_item_data['dnd-wc-file-upload'] );

    // Set Custom Price
    if( $total_files > 1 ){
        $product = wc_get_product($product_id);
        $price = ( $product->is_on_sale() ? $product->get_sale_price() : $product->get_regular_price() );
        $cart_item_data['new_price'] = ( $price * $total_files );
    }

    return $cart_item_data;
}

function set_codedropz_calculate_price( $cart ){

    // Bail early
    if ( is_admin() && ! defined( 'DOING_AJAX' ) ){
        return;
    }

    // Adjust Price only if new_price is set
    foreach ( $cart->get_cart() as $cart_item ) {
        if( isset( $cart_item['new_price'] ) ){
            $cart_item['data']->set_price( $cart_item['new_price'] );
        }
    }
}