Web shops (also called DTC stores) let studios sell currency and items through their own site, with payment processing fees generally below app-store commissions. Regulatory changes and platform policy shifts have made them far more common in mobile games.
The commercial upside is margin and a direct relationship with the player. The analytical challenge is connection: the purchase now sits in a different system from install attribution and in-game behaviour, so teams need a deliberate way to link the two to know what a player is actually worth.