[Dilettante_Pro]

Так?

$('[name=quantity]').change(function(){
   var product_total = parseFloat(price * this.value),
   cart_total = parseFloat(product_total + current_cart_total);
   if (!(this.value < 1)) {
      $('.cart .price .woocommerce-Price-amount').html( product_total.toFixed(d_num).replace( '.', d_sep ).replace( /\B(?=(\d{3})+(?!\d))/g, '$&' + t_sep ) + ' ' + currency );
   } else {
      $('.cart .price ins .woocommerce-Price-amount').html( product_total.toFixed(d_num).replace( '.', d_sep ).replace( /\B(?=(\d{3})+(?!\d))/g, '$&' + t_sep ) + ' ' + currency );
   }
   $('.price,.woocommerce-Price-amount').toggle(!(this.value <= 1));

});