Fuente: https://www.damiencarbery.com/2020/03/remove-add-to-cart-button-conditionally/

Si a veces has querido bloquear la compra por determinadas condiciones en woocommerce, este plugin es lo que necesitas.

<?php
/*
Plugin Name: Remove 'Add to cart' conditionally
Plugin URI:   https://www.damiencarbery.com/2020/03/remove-add-to-cart-button-conditionally/ 
Description: Conditionally remove the 'Add to cart' button in WooCommerce.
Author: Damien Carbery
Version: 0.4
WC tested up to: 5.9.1
*/


class IsPurchasableConditionalFiltering {
    // A reference to an instance of this class.
    private static $instance;
    // Store whether 'Add to cart' button should be displayed.
    private $purchasable;


    // Returns an instance of this class. 
    public static function get_instance() {
        if ( null == self::$instance ) {
            self::$instance = new IsPurchasableConditionalFiltering;
        }
        return self::$instance;
    }


    // Initialize the plugin variables.
    public function __construct() {
        $this->purchasable = array();

        $this->init();
    }


    // Set up WordPress specfic actions.
    public function init() {
        add_filter( 'woocommerce_is_purchasable', array( $this, 'is_purchasable_conditionals' ), 10, 2 );
        
        // Remove variations dropdown and 'Add to cart' button for variable products.
        add_action( 'woocommerce_before_single_product_summary', array( $this, 'before_single_product_summary' ) );
    }
    
    
    public function is_purchasable_conditionals( $whether_purchasable, $product ) {
        // Store the product ID as $product will be overwritten if $product is a variation.
        $product_id = $product->get_id();
        
        // Return cached result.
        if ( array_key_exists( $product_id, $this->purchasable ) ) {
            return $this->purchasable[ $product_id ];
        }

        // Only do our conditional checks if WooCommerce deems the item to be purchasable.
        if ( $whether_purchasable ) {
            $result = true;  // Default to allowing purchase.
            // Aquí puedes bloquear por condiciones de precio, tienes que decomentar el bloque de código
            // Check our specific conditions - some examples.
            /* // Product over a certain price - this must be checked at variation
            // level so do this before the $product->get_type() check.
            if ( $product->get_price() > 20 ) {
                $result = false;
            }*/
            
			/* // Aquí puedes poner las ids de productos a bloquear, tienes que decomentar el bloque de código
            $ids_not_purchasable = array ( 111, 140, 437, 1733, );
			if ( in_array( $product_id, $ids_not_purchasable ) ) {
                $result = false;
            }*/

            // If this is a variation then get the parent product so that categories can be checked.
            if ( 'variation' == $product->get_type() ) {
                $product = wc_get_product( $product->get_parent_id() );
                $product_id = $product->get_id();
            }
           // Aquí puedes bloquear por categoría, tienes que decomentar el bloque de código
            // Check if product in a certain categores.
            if ( has_term( array( 'hoodies', 'accessories', 'tshirts' ), 'product_cat', $product_id ) ) {
                $result = false;
            }

            $this->purchasable[ $product_id ] = $result;
        }
        else {
            // Store that this item cannot be purchased.
            $this->purchasable[ $product_id ] = false;
        }

        return $this->purchasable[ $product_id ];
    }


    public function before_single_product_summary() {
        $product_id = get_the_ID();
        if ( array_key_exists( $product_id, $this->purchasable ) && !$this->purchasable[ $product_id ] ) {
            // Remove the variation dropdowns and 'Add to cart' button for variable products.
            remove_action( 'woocommerce_single_variation', 'woocommerce_single_variation_add_to_cart_button', 20 );
            remove_action( 'woocommerce_variable_add_to_cart', 'woocommerce_variable_add_to_cart', 30 ); 
        }
    }
}
$IsPurchasableConditionalFiltering = new IsPurchasableConditionalFiltering;