I doubt 3D is adding even $100 at retail at this point. It's almost certainly not adding $200. When I cite those figures, it means cost to implement is in the low 10s of dollars.
I also very much doubt it comes back next year, except perhaps in limited models. 3D is not at Redbox, not on iTunes, not on Vudu (at least from what I've seen), not a priority for Netflix (according to Netflix, which is focused on 4K). It's super popular with a couple % of homes that love it and has never been used on the vast majority of 3D-capable sets sold to date.
Vizio is willing to lose that small %age of customers to make millions more in gross margin. Period.
There is no difference in HDMI cables. If you can see the picture without visible dropouts or sparklies, the cable is working at 100%. No other cable will display a better version of that picture. You're simply wrong if you think there is a better digital cable than one that is already working.