Just to give some perspective on the outrageous prices asked for printer ink: https://www.thedrinksbusiness.com/2019/07/printer-ink-costs-...

I used to refill each cartridge in my (7?) color canon printer when it ran out.

Then I gave up and would order the el-cheapo amazon refills and change all 7 at once, empty or not.

(one big change every few months instead of random refills every week or so)

Epsons can(could?) be easily hacked:

https://sagittal.org/photo/CIS/inkchip/chip.html

...which is why there are lots of aftermarket CIS units for them:

https://en.wikipedia.org/wiki/Continuous_ink_system

You could probably format your text into some very dark gray color which doesn't use cyan.

That's a logical conclusion, but many printers outright refuse to operate if any of the cartridges are out, regardless of whether the print job requires that particular color.

I'm sure many people would happily shift from printing all black, to all cyan, then all magenta (yellow probably isn't practical) in an attempt to get maximal utility out of their color cartridge otherwise.

To achieve true black, some printers also mix cyan, yellow and magenta in.

Sure they do, but they should also print the best they can given the available resources.