You can create a discount for when participants sign-up for multiple camps, sessions, events etc. It can have tiered thresholds - the more a participant is signed-up, the higher the discount tier they can reach, and the steeper the discount can become.
This discount is aware of previous orders for the a participant. For example, if there the lowest Discount Tier has a range of "5-9" items and an amount of "5," the Participant's Order History includes 4 qualifying items, and the Shopping Cart contains 1 qualifying item, then the Shopping Cart item will be discounted $25.00. This is because each item qualifies for a $5.00 discount, and the discount had not been previously applied to the 4 items in the Order History, so the total discount amount is applied to item number 5.
This discount is also aware of the Minimum Price value on the Product. So, continuing with the above example, if the Product's Price is $50.00, and it's Minimum Price is $30.00, then it will be Discounted down to just $30.00, instead of down to $25.00, so that it does not fall below the Minimum Price. We do not suggest using Minimum Price with the Discount, as will be explained in this article.
There are no System level Configurations related to this feature.
First, create a Discount - please note that for this type of Discount, the Amount field is not used because each tier of the discount will have it's own Amount that is discounted. 
Creating the Discount's Requirement
After you have saved the Discount, click the Edit Requirements button.
Click the "Add New Requirement" button.
Input a Title, choose the type "Tiered Multi-Session All (Including History) Discount," and click the SAVE button.
The page will refresh so that you can add Tiers. Click the Add Tier button.
This Discount can have multiple tiers - the more a participant is signed-up, the higher the discount tier they can reach, and the steeper the discount can become. Input values for the Low Range, High Range, and Amount:
After inputting values in to the Discount Tier fields, click the "Add Tier" button to add another Tier.
When you are done adding Tiers, click the Save button.
Below is an explanation for an example tier set above.

The First Tier has a range of 5-9 and an amount of 5. If a Participant has 0-4 qualifying items in their Order History or Shopping Cart, then no items are discounted. If they have 5-9 items, then each item is eligible for a $5.00 discount.
The next Tier has a range of 10-14 and an amount of 10. As you can see, there is no overlap in the ranges, as having (for example) "5" in both of the ranges would make calculation of whether or not the items are eligible for a $5.00 or a $10.00 discount impossible. If a Participant has 10-14 qualifying items in their Order History or Shopping Cart, then each item is eligible for a $10.00 discount.
Note: if the first tier has been already been applied to some items, then the Discount will include this when calculating the discount amount. So, if the first tier of $5.00 has already been applied to an item, and second tier has been reached, then the item will be discounted an additional $5.00 for a total discount of $10.00.
The third Tier has a range of 15-19 and an amount of 15. When the count of qualifying items for a participant reaches this tier, then each item is eligible for a $15.00 discount.
The fourth Tier has a range of 20-500 and an amount of 20. Essentially, when the count of qualifying items for a participant is over 20, then each item is eligible for a $20.00 discount.
Note: depending on your anticipated maximum purchase range for your qualifying products, your High Range value may need to be higher than the example value of "500" to create an unbounded (maximum) tier.
Like other Assignments in Configio, you can assign a Discount to a Category or to Product. When your customer purchases something from the Category (or purchases that specific Product), they will have made a Qualifying Purchase.
Navigate to Settings --> Assignments --> Categories and select the Category whose Products you would like to be eligible for the Discount. Find Discounts, drag the Discount from the Unassigned to Assigned Category, and ensure that it is set to "Apply".
To assign to a Product, select that Product, open the Assignments tab, select Discounts, drag the Discount from the Unassigned to Assigned Category, and ensure that it is set to "Apply".
To help show how this Discount works, I am using our Schedule Builder with Timeblock Products. I have two Participants. The first Participant (Kevin) has five Timeblock Products in the Shopping Cart, and the second Participant (Sarah) has four Products in the cart.
During Checkout, your Customer sees that each of Kevin's five Products are discounted by $5.00 because he has reached the first Tier. Kevin's total discount is $25. Sarah's four Products are not discounted.
Then, Sarah is enrolled into another Timeblock. During Checkout, the Customer sees that it is discounted by $25.00. This is because her first four Products were not discounted, and so the total $25.00 discount is on her fifth Product.
Continuing our example, we have added more Timeblock Products to the Shopping Cart via the Schedule Builder. Kevin has four more Products, and Sarah has five more Products.
In the Shopping Cart, your Customer will see that Kevin's four products are each Discounted by $5.00. This is because he now has nine total Products, so he is still in the first Tier of the Discount. Your Customer will also see that Sarah's five Products are each Discounted by $15.00. This is because she now has ten total Products, so she has bumped-up to the second Tier of the Discount. The total Discount that Sarah has earned is worth worth $100.00, which is Sarah's ten products multiplied by $10.00 (which is the second Tier's amount). Sarah has already received a Discount of $25.00, so the remaining $75.00 discount is spread across five Products, so each is discounted by $15.00.
A third purchase is made for Kevin. There is a single Timeblock Product in his Cart, which brings his total to ten, which bumps him into the second Tier. Your customer will see that the Discount is $55.00. Like Sarah, Kevin has a total Discount amount of $100, however Kevin has only received $45.00 for his first nine Products, so the remaining Discount of $55.00 is all seen on Product number ten.
If a Product is Refunded and Removed, then the Product no longer counts toward the Discount. So, if they had five qualifying purchases, and one is removed then they only have four qualifying purchases. Likewise, Participants can be dropped down Tiers via removals.
For example, if a Customer purchases five products to get into the first Tier, then two are removed to drop them out of the tier, and then one more is purchased, then that fourth item is not discounted. Also, there is no added fee to compensate for the first three Products getting discounted, even though the Customer is not currently in the first Tier.
This is a complicated Discount, and so here is some additional information for you to understand when working with it.