The Washington Post has a straightforward calculator to figure out how much it will cost you to cut out cable television and replace it with streaming services. Just select the features you want, and the cost on the right tells you how much. Kind of fun to click at.
There's a table at the end that shows what each device, such as the Apple TV or Roku have. I wish that got highlighted in some way, depending on what services you want. It's just a static table as it is now.
I've given a good amount of thought to quitting cable myself but never did it. I keep cable for the live sports, mainly for basketball. The NBA streaming service is fine, but a lot of the good games are blacked out, and I tried a plain old TV antenna but the reception is horrible. I couldn't get any of the major networks. And so, after all the back-of-the-napkin math, I always end up back at the beginning — keeping my cable subscription and hating Comcast.