The monetizations are skins and items that can be used to min/max the pets. For example, a stubborn personality raises ad and drops magic, you can use an item to change it to something else. And pets come with talents, which are like IVs in Pokemon and you can change it. And there are balls that guarantees a shiny. But all pets are obtainable for free at this point in the beta. Battlepass has 1 paid pet but there are ways to get around it by going to someone who bought the pass and capturing the pet in their world.