So long as we agree that your point about Prime is pure speculation and not supported by the previous price hike. The price went from $6 for a two-day shipping option to $8 for a multi-service tier that journalists call the best deal in tech. It's better than cable, better than Netflix, better than any legal content platform. It may very well go up in price, but so far it's only gone up in value and has got a long way to go before it looks as overpriced as cable.
Prime is all about expanding Amazon's massive customer base. Maybe you buy it for streaming, but since you have two-day shipping, you start doing more of your shopping on Amazon. That's exactly what I did and now I buy things on Amazon that I never would have before Prime. Or maybe you bought it for the shipping, but you check out the video service and start buying or renting movies on demand within the same app. I already used Amazon for on-demand movie renting, or I would have done that, too. Prime may not be profitable, but it's been very effective at increasing Amazon's customer base in a world where it's easier and easier to purchase anything and everything from them (I think you can now order Prime items by voice, in your home, through Amazon's Echo). Not sure what that will mean for future price hikes, but you can't just look at Prime as a video service, the way you do Netflix.
I'd say Amazon/Netflix would be more than enough for me ... if not for college football. My cable provider took away the "vacation" option, or I'd eliminate cable for the rest of the year and just watch Netflix and Amazon, with some free OTA and MLB TV mixed in. MLB TV is a wash because I'm an out-of-market fan who would need to pay for it with or without cable, and (surprise, surprise) cable's version was more expensive with less features. Also, a lot of cord cutters have made an even better realization: they don't need to watch so much TV (or any all). A lot of other stuff going on out there, and with no boob tube to waste your life in front of, you're motivated to find it.
Broadband service is a good add-on point, but it really depends upon your options and pricing. I don't think it'd be close for me: If I didn't like sports, I'd cut cable in a heartbeat and save a significant amount of money going broadband + streaming. Broadband is also partially tax deductible for me (home office) while cable is not. Pretty sure cord cutters are saving plenty of money or they wouldn't bother. And in your case, you say you're using Netflix, not sure about Amazon or Hulu, so you have to tack that right onto your total cable bill (or take it off of the $68) when comparing. If cable was giving you everything you wanted, you wouldn't be paying for Netflix.
If you can speculate that streaming services are going to jack prices, I can speculate that Internet providers will get more competition in the future - Google, cellular, satellite, whatever. Connectivity is going to be necessary for far more than just good, old home Internet and mobile devices, so I don't see cable maintaining such a monopoly on it.