Nice, thanks for the info.

I feel like 600dpi ought to be possible with a DIY setup and a good quality but not break-the-bank camera, but maybe I'm wrong?

Where I work, I am not the one who works with the photographic digitization. I know we can do 600 dpi digitization of things of this size (whether we choose to depends on the material). But I suppose our setup may cost substantially more than OP, I'm not sure, I could ask the relevant staff.