We're all reading these articles because we're excited about the future. In that context, the issues you've raised don't seem to be that big. Cost for the bill of materials will drop with mass production, and many of the major parts are already cheap.
After seeing personal computing and mobile computing revolutions unfold during my lifetime, I'm pretty sure the technical obstacles to making a reliable and cheap oven that Myhrvold describes are surmountable. Electric cars, jet planes and search engines deal with much harder engineering challenges.
There are financial system problems. If we don't value engineer our products to rapidly fail, the mfgrs will go out of business and we won't have any ovens.
So imagine a "super oven" that is rust proof and thermal shock proof to tolerate high humidity cooking. Someone is going to figure out that running that dude dry means it'll operate theoretically for 500 years, and 90% of the home cooks will be too lazy to ever fill the distilled water tank anyway, so 50 years in or so, that mfgr will go out of business, and no new ovens.
There are some examples in the automotive world, where in the old days when farm trucks were really farm trucks and not marketed as a macho station wagon for starbucks runs, some people bought them for 100% asphalt use anyway, because they'd last 25 years if treated better than farm trucks. That value engineering epic fail has been fixed for decades now, but in the old days this was a serious problem. Ford had no problem selling commuter cars that would rust out and require replacement in 3 years but they couldn't figure out how to keep farm trucks on the farm and off the roads for 20 years, back in the 70s.
After seeing personal computing and mobile computing revolutions unfold during my lifetime, I'm pretty sure the technical obstacles to making a reliable and cheap oven that Myhrvold describes are surmountable. Electric cars, jet planes and search engines deal with much harder engineering challenges.