Gacha or Loot box mechanics is a system that is very common in most free to play games. The ability to create the illusion of the optics of obtaining a highly valued item in the game at such a low value, it's sure to get a % of players enticed in the idea of the concept.
I’ve worked with many designers that understand the concept of gacha / lootbox but not necessarily understand how to design one.
First and foremost, its important to establishing your price points.
Rarity Drop Rate Approach:
The first step in designing out your drop rates is to establish what the price points are for each rarity in the game. Assuming there are 4 different rarities in the game (Normal, Rare, Epic, Legendary)
Let’s say for example that you want to value each rarity card as a specific value.
(Note: This is not how I would do it, but i made the numbers round for easier math)
Let’s also say that my gacha box contains 100 items inside the box.
The rarity distribution will be as follows:
With the cost per rarity you are able to define your drop rate can be broken down by establishing the cost per pull.
Lets for convenience sakes set the cost for 1 pull of the gacha is $5
If you want to set the value of your legendary gacha at $500 (like the above example) than the drop rate has to be
Drop Rate = Cost of Gacha / Cost of Legendary
Drop Rate = $5 / $500 = 1%
This means that you have a 1% chance of getting a legendary card but which one can be based on how many you created and distributing out the 1% with all your cards.
So in this example, you have 5 (5% Legendary = 5 Legendary Items) cards that are legendary out of the 100 you have created. Therefore there is a 0.2% chance that you can get a specific legendary card.
Meaning the value of a specific Legendary card can potentially balloon up to $2500.
This is the Rarity Drop Rate Approach that I commonly use to setup my gacha drop rates thats based around the cost of each item I create in my product.
Item Drop Rate System
This is a very simple approach where you are required to define the rarity of each individual item providing you with the flexibility of setting the absolute value of each item in the game.
A bit tedious but this is dependent on what type of game you are making. I would suggest for a card collection game you design around the rarity drop rate system as the expectation is to inflate the rarity pools meaning the liveops team will have a lever to increase the cost of ‘each’ individual card. All this will depend on your morales and your monthly revenue targets.