The aggregate of all these fees (plus Netflix, Amazon, etc) will likely approach or exceed the cost of a typical cable subscription.
Also, having all the video in a choose-it-myself format avoids droning out in front of the TV for hours just watching commercials and reruns. And getting it over an IP network means a lot. Hello logging! Hello filtering per MAC around homework time!
The single-service cost of any one of the most popular services will likely approach or exceed the cost of a typical cable subscription while providing far less (but more focussed) content.
1) the broadcaster is a step removed from the cable operator (though with all the mergers in the content/delivery space, they might be part of the same parent company). If Netflix develops a new show like House of Cards, they know exactly how many people watched it for how long, etc.
A cable company might track what station their customers are watching but unless they are reporting that back to the broadcaster it won't change programming in the near-term. It may make the cable company make different decisions about their lineup but such decisions are often part of many-year contracts with forced bundling (eg. Disney saying you must carry all these stations if you want ESPN) so even if they do have data I doubt it has much impact.
2) The cable company can know what channel your settop box is tuned to, but a lot of people have setups where the cable box is essentially always on (and only the TV is switched off) and there is no reasonable way for the cable operator to know if anyone is actively watching or not without resorting to very imprecise heuristics like only counting it if the channel has recently been changed.
This is unlike Netflix, et al, which have less passive interfaces where you can be more reasonably sure that if the user started some content they are actually watching it and not streaming it to a TV set that is off.
1) There's obviously a lot more separation here, but it's worth noting that there is a lot of data out there available to broadcasters that doesn't come from Nielsen, such as broadcasters licensing data that comes initially from cable providers. The number of set top boxes here dwarfs the size of the Nielsen data set.
2) You can get more precise if you want. At a basic level, you can look at a lot more options than just changing the channel. You can also train models based on the overlap with something like Nielsen where you have more information about when they are watching. If you can match up comcast data to Nielsen data, you can build a model for active vs. inactive boxes on the comcast data.
3) To backtrack a bit, the fact that Nielsen is a "very small subset" as you said a couple of comments ago is relevant for some things but not others. For the broadcast network prime time shows, it's certainly a big enough sample to see which shows are popular among what demographics without having the level of detailed information that Netflix or cable operators have.
All in all, I agree with you that there is more separation and it is harder to use, but there's still a key distinction between Nielsen, which is in something like <~0.1% of homes and the other data sources which are many times larger. They don't all seek it out, but it's possible for broadcasters to acquire the sort of data necessary to answer questions about content popularity like Netflix can consider.
There's plenty of wiggle room here for HBO, and because it's more a la carte, I could easily drop a couple of things there once I have HBO.
Not sure what they'd charge for standalone HBO yet, but I think it could be as much as $50 a month and I'd still come out ahead (especially if I dropped something). I got rid of comcast a while ago. As I recall, if you get the minimum level of cable service required for HBO plus specific surcharge for HBO and your internet service through them, I think it's was over $120 a year… I know I'm being vague, but that's largely because comcast doesn't really want to make it easy to figure out what things cost, though, and you can play various games (threaten to quit and get a deal that they hope you won't notice when it expires)… but they weasel right back and get you on all kinds of little things, though, so you have to pay close attention to your bill.
Also, every now and then comcast will tell you to return something like a cable box, and then claim you haven't returned it, and send you a letter threatening your credit history if you don't pay for not returning it even though you have, and then ask you why you're quitting. So you have to factor in that extra cost too.