Not sure I understand the question - IAP involves tiers with preset pricing. Pretty sure it's possible to know that ahead of time. Devs are not free to casually ad-hoc their own app/IAP pricing.
As far as pre-paying for service, you'd perhaps want to use tokens, where the user can buy them in various increments, redeem them as they go, and you decide if they expire, etc, tracking their use/consumption via receipts.
Might want to move this the IAP forum - see FAQ#2 here:For Best Results - Read the Label
I appreciate it greatly. And sorry for any lack of clarity. You're correct on the IAP pricing. We're contemplating freemium model. So the subscription portion of the IAP is known. In addition, there's an opportunity for a service that is a la carte or on-demand, where the exact price of the service isn't known until its completion. That was the charge I was having a hard time with how to bill for, give that it's not a known amount until after the service is engaged in.
I thought about tokens, to your point. That is a good idea and I'd originally stayed away from it given, to your point, you need to keep track of use/consumption via receipts (which could be tough with scale, if there's not a system in place to help manage.
I so appreciate the reply and will dig into Tokens more, since I don't think there's any possible way to charge for a service unless you know the exact amount up front.
Kindest thanks and of course very grateful. Let me know if you disagree with any of my sentiments above. Working hard to engage with the docs and sometimes the dialogue helps where it's not quite clear. Thank you, KMT!