[juiyout]

In your vending machine example, it is a transaction, not a tax, as you implied and I agree. However Apple taking cut of app's revenue is awfully a lot like corporate tax.

[oneplane]

In that case are transaction fees for credit cards also tax? Or PayPal fees for that matter? Or fees for using platforms like eBay and Aliexpress?

[Dylan16807]

Yes, I'd call any small mostly-percentage-based transaction fee that a platform imposes a "tax" or "platform tax".