Abbyy, and most good commercial OCR, charge a runtime royalty based on the number of cores you are deploying to. Depends on volume.
And the kicker: You can't buy those licenses from them directly. They put you in contact with some randome monopoly local distributor that usually has mandatory "training" charges.
Messy, and I'm planning on staying away from that with a ten-foot pole.
All do-able within Linux.
I seriously doubt that it's just $100 -- but, I guess if you are making an application that you are just going to run yourself on a single machine, it would not cost much. The costs tended to increase with the number of computers you were deploying to. Or perhaps we used something more capable (does that come with all languages -- including Chinese/Japanese/Korean and RTL languages).
What kind of problem were you dealing with? Were you bumping up against any constraints?
I think we opted for the customer actually obtaining their Abbyy license from Abbyy in the end because of the licensing mis-match. We sold just the wrapper.
Our parent company was a big user of Abbyy, and I think had a totally custom deal. They needed it for all of the language support and similarly wanted the full power to run it at high-speed and inside of .NET programs.
They also sold Recognition Server which has fewer options to integrate with programmatically (it was only 'hot folders' at the time), and I think only runs on Windows, but costs less.
And their mobile OCR which is lightweight, designed to run on smartphones, they worked out deals where they get a percentage of revenue.