When I needed to scan a few thousand pages from books about a decade ago, I got a surplus Fujitsu M3093DG flatbed scanner and axis scan server from ebay. Cost was under $200 for both. This particular scanner scans a page in 1.6 seconds so is much faster than my old epson 1640XL B size or a fujitsu snapscan scanner. It took about as much time for me to flip the page on the book and position it as the actual scanning.
https://www.fujitsu.com/downloads/COMP/fel/support/scanner/manuals/M3096gx-93gx-93dg.ome.en.pdfhttps://www.axis.com/files/datasheet/700/700_eu_ds.pdfPS. I have a stack of those axis scan servers and would be happy to send one if provided a shipping label.