Printer Bob wrote:

In reality it's the major independant printing ink manufacturers that
make OEM ink for printer makers. But contracts stipulate they cannot
legally sell this "branded" ink to the general public or to the
aftermarket ink dealers. So they alter the formulas slightly, it's no
longer "branded" ink and it becomes "aftermarket" ink. Slight change in
formula (with no big name attachment) and huge savings for the general
public.

As I suspected. It's rather like the choice in a supermarket between
branded cornflakes like Kellogs and the supermarket's own brand - both
made by the same company, the difference being indistinguishable except
for the price and pretty packet.

Jim Ford