WooCommerce: Add product to cart with price override?

I have tried all above code samples and latest woocommerce 3.0 is not support any of the above example. Use below code and working perfectly for me.

add_action( 'woocommerce_before_calculate_totals', 'add_custom_price' );

function add_custom_price( $cart_object ) {
    $custom_price = 10; // This will be your custom price  
    foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
        $cart_item['data']->set_price($custom_price);   
    }
}

You need to introduce an if statement for checking product id, in above code:

add_action( 'woocommerce_before_calculate_totals', 'add_custom_price' );

function add_custom_price( $cart_object ) {
    $custom_price = 10; // This will be your custome price  
    $target_product_id = 598;
    foreach ( $cart_object->cart_contents as $value ) {
        if ( $value['product_id'] == $target_product_id ) {
            $value['data']->price = $custom_price;
        }
        /*
        // If your target product is a variation
        if ( $value['variation_id'] == $target_product_id ) {
            $value['data']->price = $custom_price;
        }
        */
    }
}

Add this code anywhere and make sure that this code is always executable.

After adding this code, when you'll call:

global $woocommerce; 
$woocommerce->cart->add_to_cart(598);

Only this product will be added with overridden price, other products added to cart will be ignored for overriding prices.

Hope this will be helpful.

After release of woocommerce version 3.0.0 product price is update on add to cart using set_price($price) function. The example is given as below :

add_action( 'woocommerce_before_calculate_totals', 'mj_custom_price' );

function mj_custom_price( $cart_object ) {
   $woo_ver = WC()->version; 
   $custom_price = 10;
   foreach ( $cart_object->cart_contents as $key => $value )
   {
       if($woo_ver < "3.0.0" && $woo_ver < "2.7.0")
       {
           $value['data']->price = $custom_price;
       }
       else
       {
           $value['data']->set_price($custom_price);
       }
   }            
}

Many Thanks

Here is the code for overriding price of product in cart

add_action( 'woocommerce_before_calculate_totals', 'add_custom_price' );

function add_custom_price( $cart_object ) {
    $custom_price = 10; // This will be your custome price  
    foreach ( $cart_object->cart_contents as $key => $value ) {
        $value['data']->price = $custom_price;
        // for WooCommerce version 3+ use: 
        // $value['data']->set_price($custom_price);
    }
}

Hope it will be useful...