You can configure your group registration products with global bulk discounts, product level or disable them altoghether.
Global Discounts
Visit the Group Registration settings page from LearnDash LMS -> Group Registration Settings.
On the general settings tab you will see the Bulk Discounts at the end, enable it.
Global Bulk discounts allows the administrator to configure percentage discounts to be applied on all the group registration products.
You can add 1 or more discount rules for the percentage discount to be applied against a minimum quantity of the product purchased.
Note: You cannot have more than 1 rule with the same Minimum Quantity.
Product Specific Discounts
Similar to global bulk discounts, you can configure discounts for specific products for which you may change the discount settings as compared to the rest of the products or disable them for that product.
As per your need set the Bulk Discount Setting while configuring the product.
When configuring bulk discounts you have an additional option to configure bulk discounts either on percentage or a fixed amount.