You could throw them up on eBay and see if anyone bites. I sort of doubt they have any real value since the printers they work with are 20 years old and too slow to really be practical for modern graphical work, but they might have some appeal to certain diehard niches. Some Wordperfect fanatic might take them off your hands.

(Postscript emulation cartridges used to be pure gold for making good use of a LaserJet II-series printer under WordPerfect 5.1 for DOS. Wordperfect had sophisticated page layout/formatting capabilities but was limited to using whatever fonts/sizes were present in the printer. A Postscript cartridge gave you scalable fonts, and thus free reign to format pages however you wanted. They weren't as big a deal with an LJII since PCL5 added Intellifont scaling.)