Opportunity Costs. Now this is one aspect of costing that’s a bit more difficult to compute for. Opportunity cost basically refers to the money you could potentially earn or gain if you were doing something else. For instance, instead of earning $2,000 a month from ads on your blog, you could be earning $6,000 per month working as a designer or a developer at a local company. So the opportunity cost here is $6,000 less $2,000, which amounts to $4,000.

Chances are that if you are running a site capable of generating that much ad revenue, you are already at the point where you could start earning money by writing books and doing other work.

How much is your time worth?

You also forgot the licenses for PhotoShop, Premiere, iWorks, iLife, MS Office, etc. How about other devices such as cellphone bills for 3G, digital camera, scanner, printer, etc?

And yes, I think it’s harder to compute for the actual cost of blogging this way. Maybe I can also compute for it as a fraction of my total time working on computers and being online. Hey, I’m an economist, but accounting is perhaps one of my worst subjects! :)

And not to nag, but my name is Paulo, not Paolo. As awesome as it would probably be to be Italian, I’m from Brazil and that’s how we spell it here.

At any given time, I usually have two or three computers in front of me doing different things. One might be uploading files on FTP, one might be for reference, and another would usually run the word processor or the actual blog post window.

And yes, two of my laptops came without bundled OSes. I bought a copy of Vista for one, though, and XP for the other. At one time or another, I’ve used a flavor of Linux as my main work OS, but these days, it’s just Windows and OS X for simplicity’s sake. I just can’t stop tweaking and hacking on Linux, and it affects my productivity! :)

There’s a few problems with your calculations. You assume that the only thing you use your computers and Internet connection for is blogging. In reality, you’d have to calculate a fraction of the hardware, software and DSL subscription based on what portion of your use of these items is devoted to blogging. If you’re reading XKCD, CNN.com or browsing YouTube, for example, you’re using the computer, are logged into Windows or OS X, and are viewing the website thanks to your DSL connection, but not for the purpose of working on your blog. Also, you don’t need more than one computer for blogging, even though you can use all of them to do so. If there’s more than one on at the same time, chances are only one of them is blogging and the other shouldn’t be counting towards your blogging expenses, unless it’s being used in some auxiliary function (like displaying a reference text, though you could use only one computer and alt+tab between windows). It turns out that even if you do spend most of your “connected time” blogging, you can still get a substantial reduction in your monthly blogging cost, since the hardware and operating systems are the greatest portions of the overall cost.

And while this amounts to a personal preference (but then again so does the choice of what blogging software and domain provider you use, as well as what kind of hardware you buy), you can buy a PC without Windows pre-installed (though you can’t get a Mac without OS X) and install a free operating system, like some flavor of Linux, BSD or Solaris. This would slice off the imputed cost of bundled software, not to mention (for me at least) the time I’d spend formatting my computer and installing Ubuntu Linux anyways, during which I’d be using up electricity.

There’s lots of other ways to make small cuts. For example, if you’re really cheap and live at a walking distance from a café with free Wi-Fi, you don’t really need DSL in theory (though the feasibility of this plan is questionable).