More modules come to XforWooCommerce family. Meet Package Quantity Discount for WooCommerce.
This module can set discounts per cent or fixed for your products on set quantities.
Secondly the option for Select Box with packages is available, so you can show it with options such as 6x$9.99, 12x$9.99 instead of the plain quantity input. The quantity input doesn’t even have to be used at all.
Plugin is capable of assigning different settings to condition such as tag or category within the product.