Hey Russell,
Good question! Unfortunately, neither Event Ticket nor Event Tickets Plus are capable of providing deals or promotions for ticket purchases.
That said, it’s very possible that the e-commerce plugin you use with them is capable of doing that. For example, if you use WooCommerce to take payments, then it might be able to extend it’s features to tickets, since tickets are simply of registered product in WooCommerce. Although I have tried it myself, the Smart Coupons extension for WooCommerce looks promising and worth checking out.
Cheers!
Geoff