Comment by hamrickdavid

In-App purchases are for digital goods only (Content, Functionality, Services, Subscriptions). You are completely free to sell real/physical goods (ie. a train ticket) via your own payment system.

https://developer.apple.com/appstore/in-app-purchase/In-App-...

"You must deliver your digital good or service within your app. Do not use In-App Purchase to sell real-world goods and services."