[jeroenhd]

Printheads are nanotechnology with extreme precision requirements. The rest of the printer is a few well-timed stepper motors, simple in comparison. HP cartridges including the printheads will take a lot of complexity away from the open design.

In theory you could probably modify one of these by grabbing an HP cartridge and slapping an ink tank on top with the right sponge for transferring the ink over. Selling parts from HP printer cartridges might creep a little too close to HP's patent lawyers, though, and having users open cartridges to extract the print heads themselves sounds like a messy solution that would reduce the appeal.

I'm sure that given time, someone will 3D print an ink tank holder that will let you use cheap ink supplies through the expensive HP cartridges.

[whyoh]

>HP cartridges including the printheads will take a lot of complexity away from the open design.

Yes, but it also means it won't be cheaper or more reliable than a regular printer. The print head is what fails most often and you'll still have to buy a new one.

[dymk]

Aftermarket ink cartridges that are HP compatible are quite cheap compared to brand name

[whyoh]

Those are made from used HP cartridges, so they have a shorter life span.