Know of a fast black and white scanner?

[Bob]

Something that could do 300-600 dpi in less than 20 second/page?

[thalbergmad]

My Mustek Pro can do an A3 sheet of piano music in less than 20 seconds at 400dpi.

Thal

[quantum]

If you are doing a lot of pages and it isn't something you could typically put through an Auto Document Feeder, you may wish to consider a digital camera with one of these setups:
https://www.diybookscanner.org

It is considerably faster if you are doing hundreds of pages.  IMO, it is worth the time to setup if you have lots to scan. 

[Bob]

That's the idea.  Quick and cheap.

I'd have to buy cameras and build some book cradle for the DIY book scanner though.  Plus software probably.  Those do look super fast. Maybe a paint by number type of DIY would work, except those can get expensive too.

[quantum]

Look around in their forum.  There are recommended older cameras that can be found cheaply.  

If you want a quick and dirty setup, you may already have some of these things:
Camera, tripod, table, one of the workflow software packages.  

[Bob]

I got confusified.  Haha.