Dave, I agree I hate throwing away anything useful, but in this case they will clog up the fins in the feed, yes they will write but even with an upgrade nib they cause problems because of the inconsistency of the volume of the ink. I just want to give my customers the best experience possible and with these I'm falling short of that goal.
Maybe we should clarify "cartridge" Roy.
It sounds like you're thinking of the cartridges on the fountain pens (they will clog up the fins in the feed), whereas I was thinking in terms of the Parker and Cross style ballpoint cartridges that come with the kits.
In terms of the Fountain Pens I'm selling, I send the stock in cartridges along with the pen (guess maybe I should stop that), but I make sure I've included a converter if it doesn't come with one and I package a small bottle of Private Reserve ink the get the buyer started with a choice of black or blue. If they don't want it I'll offer a discount.