In the current version of , you cannot buy loot boxes with real-world money or in-game currency . They have been reintroduced as a non-monetized reward system to make the game feel more rewarding.

Currently, there are four main ways to acquire loot boxes on PS4: Loot Box - Overwatch Wiki

Instead of purchasing them, you can earn various types of loot boxes through active gameplay and participation in community events. How to Earn Loot Boxes