[WalterBright]

Double-entry bookkeeping was a great advance.

[ezekiel68]

And -- in keeping with the flow of this thread -- a complete luxury until the implements (paper/pens/tape/disk/silicon) would become abundant and ubiquitous.

[WalterBright]

Paper and ink were good enough for centuries.

[dTal]

Paper especially was very expensive until approximately the 19th century.

[WalterBright]

The explosive growth in the printing industry suggests otherwise.

[ezekiel68]

We are simply pointing out there was a time when the surface one could write on was so precious, people used to cover previous works and re-use it instead of obtaining new ones (vellum, etc). So -- you're not wrong about the explosive growth. We're just pointing out the abundance of even writing instruments occurred at a certain point in history.