I'd be curious to see if any of the low-cost ink manufacturers for fountain pen ink branch into inkjets, with this development. Both being water-based and having constraints around lubrication, flow, penetration, dry time, etc., I wouldn't be surprised if there were a fair bit of room for knowledge (and chemistry R&D, for a shop with a wide enough range of ink properties) to translate.
Buying bottled ink is already the cost-effective option for folks writing the old-fashioned way -- the equivalent to a sub-$20 4.5oz bottle of waterproof fountain pen ink (current price for a large bottle of Noodler's Heart of Darkness, 8/4/2015, is $19) would, if purchased in rollerball refills, be in the range of 76 to 82 pen refills, priced from $1.66 to $3.20 each; going the bottled route is vastly saner for folks who are willing to buy several years' worth of ink at one go.
(Up-front costs to use bottled ink aren't that high either -- excellent sub-$30 pens include the TWSBI Eco, Pilot Metropolitan and Lamy Vista).
But then -- with an extra-expensive printer, perhaps simply voiding the warranty if someone used a competing ink would be enough to prevent customers from trying to cut costs there. Hmm.