"The cost savings is great, but isn't the biggest driver for me, it's mainly the principle that I don't own the device I paid for, and I'm really tired of having cat litter everything in my home."
So exercise your rights as a consumer to research beforehand and not buy it. Or return it. Or modify it, as you have. Or, for god sakes, ask your vet or friends with cats or reddit for advice on having cat litter everywhere (I believe the most common solution is a covered box with fairly high side.) You can also teach your cat to pee/crap in the toilet, believe it or not. There are little "litter box" inserts that reportedly make it pretty easy; the cat goes "oh, another litter box" and uses it for a week or two, and then you remove the insert, and if the cat notices, they go *shrug* and still use it. No more litter, no more stink.
But for god sakes....I was around on Slashdot when the fist inkjet printer companies started chipping their cartridges. I also learned about Gillette in...either middle school or high school. That was a century ago, if not more. The "handle is free, the blades are disposable and we have a very healthy profit margin on them" model is quite, quite old. Why are people surprised? Especially if you read Slashdot, why didn't you do research on it?
Your robotic, do-everything catbox would've cost substantially more if the company were not figuring on a continuing revenue stream. In fact, it might have cost so much that nobody would've bought it.