In-App Payments
Not available today
AppX does not build payments into apps today. The AppX changelog will say when it is available.
Most apps that charge money use one of two models.
Subscriptions and in-app purchases
For apps that sell through the App Store and Google Play: subscriptions, one-time unlocks, and consumables. They need a paywall screen, purchase and restore flows, and a check of what the user has paid for.
Direct card payments
For apps that take card payments directly — marketplaces, on-demand services, e-commerce. They need a checkout flow: card entry, payment confirmation, and saved payment methods.
Until then
AppX can build the screens (a paywall, a checkout form) as ordinary screens, but it does not take real payments. Your app is a standard Expo project, so you can download the code and add a payment provider yourself.