Hi Mike,
Thanks for your interest in our plugins!
Event Tickets Plus is compatible with both WooCommerce and Easy Digital Downloads. In both cases, tickets essentially map to regular products (or ‘downloads’, to use EDD parlance).
That to say, the full range of possibilities that those plugins open up are mostly available to you when you sell tickets. I could certainly envision a discount being applied automatically during checkout if a certain quantity of products is purchased, but the means of implementing this will vary and depends not just on the specific ecommerce plugin you use but of course your own vision of how this should work.
That to say, this is definitely possible – but there are parts of the puzzle we’re not best placed to answer 🙂
I hope that helps, but let me know if you have any other questions.