Uncovering and explaining how our digital world is changing — and changing us.

Last year, for the first time, you could buy HBO on the Web without paying for any other cable TV. That was a really big deal, and something that didn’t seem possible just a few years earlier.

So now lots of people assume that the rest of the TV grid is going to go “a la carte,” too.

Don’t hold your breath. While HBO went off on its own much sooner than most people thought, it will be very hard for the rest of TV to follow suit. That’s because the TV model is based on the bundle — the idea that when you pay for TV, you get the channels you want, and lots of other channels you don’t want.

What’s that? You don’t care about what the TV guys want? You just want the TV you want?

Alright. Let’s play along. Short answer: You’ll pay a lot more for the TV you want.

Here’s a chart, via MoffettNathanson analyst Michael Nathanson, that tells you how much you’d have to pay to get some of the top TV networks on their own — if the networks wanted to replace the money they make selling their stuff wholesale to pay TV providers like Time Warner Cable.

Two important things to factor in here:

Note that the chart doesn’t include broadcast networks like CBS and Fox, which are technically available for free over the airwaves, but in practice now get hefty per-subscriber fees from the cable guys as well — now approaching a couple bucks per person. That price gets marked up and passed along to you, the pay TV subscriber. Factor in those networks and you can see why Apple has spent years struggling to get a $30-per-month Web TV package together.

It’s not a coincidence that the two most expensive networks — ESPN and TNT — are the ones that have spent the most on sports programming (you should throw in TNT’s sister network TBS to get a fuller picture, while you’re at it).

In fact, you might argue that the chart above should be titled “Look How Expensive Sports Are.” Which we always knew but is always worth pointing out again.

Or here’s yet another alternate title: “Is There Any Practical Way to Imagine ESPN Going the HBO Route?”

Which, not coincidentally, is one of the things I plan to ask ESPN boss John Skipper about next month at our Code/Media conference. If you haven’t bought a ticket, you can do that here.