Filter / function for the Woo Commerce plugin (wordpress). If no price is set, let's output a custom Call For Price (or whatevers). Goes in /woocommerce/woocommerce-hooks.php, but should also work out in your functions.php. Saw that a few peeps created plugins for this idea, but that's kinda retardery, since it's such a simple and tiny solution.

Woo Commerce Call For Price

/* Call for price filter */
add_filter('woocommerce_empty_price_html', 'custom_call_for_price');
 
function custom_call_for_price() {
     return 'Call for price: 1-800-your-mum';
}