Oh I'm sorry, I forgot that provider API's are magical, mythical beasts that must be tamed from an intermediary server, never from a client.

It's OK to say "we don't think enough people will pay enough for a one-time purchase to cover development costs". You don't have to invent some kind of technical reason for it to be a service.

But having said that, I cannot believe that companies would pay the amount you're asking for a service either.