Prova così :
codice:
 <?function members_only_price($price){
if(is_user_logged_in() ){ 
   return $price;
}
 else{
remove_action('woocommerce_after_shop_loop_item','woocommerce_template_loop_add_to_cart' ) .remove_action('woocommerce_single_product_summary', 'woocommerce_template_single_price', 10 ) .remove_action('woocommerce_single_product_summary','woocommerce_template_single_add_to_cart',30 ) .remove_action( 'woocommerce_after_shop_loop_item_title', 'woocommerce_template_loop_price', 10 ) ;
 return   '<a href="' .get_permalink(woocommerce_get_page_id('myaccount')). '">Accedi</a>  o   <a href="'.site_url('/wp-login.php?action=register&redirect_to='get_permalink()).'">Registrati</a> 
per visualizzare i prezzi!'  ;  }
}?>