If you are thinking of offering a promo code to your customers to give them access to a cheaper ticket here is a step by step how to do it:
1. You should create a new ticket with the final value with the promotion
2. Click on Advanced settings and you should set the limited visibility
3. Put the word you want to use as promotional code in the Access Code and save it
When your customers go to make the purchase, they have the option to enter the code and only then see the cheapest offer.
Watch this video to make it easier