The real expense is in the data centers/hardware.

The cost of the books is negligible in comparison.

Somewhere a gritty warehouse in a developing country is receiving shipping containers of old books, massive teams manually flipping each page as a 2nd hand Canon digicam takes a pic of each page, to be OCR’d by the same AI being trained.

Once the book is done, 99% of them go into the furnace at the district heating boiler next door. The other 1% back to a developed country for resale.