PHP if product price is 0 in cart

Hi
I have this PHP-code:

add_filter( 'woocommerce_package_rates', 'custom_shipping_settings', 10, 2 );   
function custom_shipping_settings( $rates, $package ) {
   $shipping_class_target = 143; // shipping class ID (to find it, see screenshot below)
   $in_cart = false;
   foreach ( WC()->cart->get_cart_contents() as $key => $values ) {
      if ( $values[ 'data' ]->get_shipping_class_id() == $shipping_class_target ) {
         $in_cart = true;
         break;
      } 
   }
   if ( $in_cart ) {
      unset( $rates['flatrate:1'] );
   }
   return $rates;
}

The above code checks if a particular shipping class is selected. Instead, I would like to check if a product in the cart has a price of 0.

Is it possible?

As a test, I have tried with:

if ( $values[ 'data' ]->get_product_price() == 0 ) {
     echo '<script>alert("It works");</script>';
 } 

… but it does not work either

I really hope someone can help! ??