If there are only a handful of operators in a given industry and they use the same billing format, why not?

Create a known good OCR to calculation mechanism, then generate reports based off it. If it is inaccurate, its probably a small amount of logic to fix it.

With GPT you could even get it to write the parsing logic for you perhaps, and maybe process bill data when a bill doesn't exactly match existing parser data.

Reminds me of Mechanical Turk's old tagline: "Artificial Artificial Intelligence"