For kicks, I signed up Chamber Four on Kindle’s new blog publishing platform. (You can sign up your own blog here.) You can find C4 at the Kindle Store, but, whatever you do, don’t buy it.

Buying free blogs for your Kindle isn’t just a horrible scheme (Amazon keeps an eye-popping 70% of the $1.99 per month most blogs cost), it’s also one of the most expensive ways to buy bandwidth.

According to my very conservative estimate, paying Amazon to put a free blog on your Kindle is only worth it if the blog publishes at least 400 posts per day. That’s right: it’s only worth buying blogs that publish at least 400 posts per day. This makes Amazon’s “free Whispernet” by far the most expensive way to read this or any other free blog.

There are several ways to get any free blog on an ereader, for free. You can use Mobipocket Reader to package any RSS feed (like ours, or the New York Times‘s) for a Mobi-based ereader like BeBook, or you can use Calibre to package RSS feeds in ePub or LRF format for your Sony Reader.

If you want more convenience, an RSS aggregator like Google Reader can collate all your feeds into one handy page that you can access from a computer or a smartphone.

Whatever you do, don’t pay Amazon for free content.

After the jump, I’ll show my work on that 400-posts-per-day figure, and link to some related stuff.

400 posts per day

OK, so Amazon charges $1.99 for many blogs (although, they’re already cutting prices). They keep 70%, or $1.40. Of the Bezos cut, we’ll say 40 cents goes toward website mainentance, databases, etc., which  leaves $1.00 for Whispernet charges.

How much does regular bandwidth cost? You can get an unlimited Verizon internet-everywhere card for $60 a month. For the sake of argument, we’ll say they put a 250 GB/mo cap on your bandwidth, like the cap Comcast put on its Internet service last October. That’s 4.17 GB of bandwidth per dollar.

So how many web pages is that? According to this report, the average web page size in 2008 was 312 KB. That’s probably an overestimation for something like a text-centric blog, but we’ll round up. Let’s say you get 3 blog pages per megabyte of bandwidth.

That means that, with an expensive internet-everywhere card, and a fictional cap on bandwidth, you should be able to buy 12510 web page views for one dollar. That works out to over 400 every day of the month.

Even with the price reduction on some blogs to $0.99, the Whispernet route is obscenely expensive. It makes more sense with the New York Times and other large organizations, which are presumably getting a bigger cut than 30% and publish a lot more premium content. For free blogs, though, paying through Amazon amounts to Bezos and co. yet again playing both ends against the middle.

Other tidbits about Kindle and blogs

So all this math is an argument against readers buying blogs on their Kindles. But the blog publishing platform also seems to be a really bad deal for bloggers.

Mark Athitakis isn’t putting his blog on Kindle, and he cites this piece by Edward Champion as his rationale. Champion details the appalling fine print Amazon wedges into the blog publishing contract, in particular the rights bloggers sign away when they publish for Kindle (pretty much all their rights).

Elsewhere, the publishing platform is receiving less staunch opposition. There was a mild debate on GalleyCat last week, and the Literary Saloon is compiling a list of literary blogs available on Kindle.

Essentially, the whole blog on Kindle thing seems like a neat idea with bizarre legal nonsense tacked on, and a ridiculous monetization scheme that pretty much makes the whole thing worthless.

I signed Chamber Four up to see what the process was like, but after the horrors of that contract, it seems like there’s a lot of downside and very little upside.