I'm trying to determine how services such as park mobile avoid the 30% transaction fee that apple imposes. Is it because parking is a physical good?
Apple specifically precludes anything that can't be delivered via the app from using in-app purchases. So you're free to tie a credit-card to services and real-world fees (think Uber) without paying Apple any transaction fees.
Here's Apple's documentation on what they support (and don't allow) for in-app purchases.
Happy to help in any way I can. I run a mobile-based startup myself.
I've had my app rejected for not using Apples In-App Purchase (IAP). Essentially, anything that can be delivered via the app that's "digital content" is taxable.
Originally Clarity connected the calls through the app vs. The conference line we use today - once we made that switch we were good to go.
So physical items should be fine.
Also, we use Stripe.com to process credit cards if that helps.
Any transaction that Apple processes for you will be subject to the 30% transaction fee. Any direct "in app purchase." If you have a basic eCommerce app where you sell physical products but you yourself process the payments, Apple will not take 30%.