And $20,000 to get someone who knows how to install such a system to do the job.
Then whenever a significant change is required, you need to call back your "expert". New location? xk$, etc.
But I think the biggest concern is that suddently the owner does not understand how his reversation system works. He used to be able to call Joe and know what's going on...
Web systems are almost never built for productivity.
The issue isn't universal API, but universal data models which is probably impossible.