[cwillu]

Inkjet cartridges often contain the print heads; toner cartridges still need a fuser roll and imaging head to do anything.

[exmadscientist]

Part of my point is that making a print head driver is, in general, harder than making a laser imaging head. A lot harder.

Of course the details of what specific parts are purchaseable on the open market can and will change this calculus a lot.