They could probably make knockoff LaserJet IIIs, but nobody wants enough to fire up an entire line.
I'm sure the same factories could make zero-margin laser or inkjet printers, but why target a shrinking, obsolete market when you could use the same employee expertise to build things for growing, high margin markets?
I'm guessing buggy whip and carriage bolt manufacturers charged crazy markups for 10-20 years after the Model T came out. I think we're witnessing something similar (especially for inkjets that target document sized printouts).
1. Parts
2. Various cheap items without brands
3. Obvious "overruns" of a branded factory smuggled out the back door
4. Additional runs of a factory that is no longer making whatever it was for the original manufacturer
5. Supplies
You find some printer stuff in 1 and 5, and I saw a few that might be 3 or 4.
Nobody in China is bringing up ancient equipment lines (and it would likely be way more expensive).
At most, you might be able to find someone somewhere (if you have the right connections) that can get you a default firmware for some known printer that is OEM'd to everyone. I know these have been found for things like smart bulbs and other firmware'd devices.