Blogger, Google's hosted blogging platform, offers what is probably the cheapest cost of entry into blogging. As in zero. Free blog hosting, and you can still make money from it (although let's face it, very few people really make that much from their blogs.)
Really big blogs may eventually move off to other platforms, like WordPress or Moveable Type, where they have more control over options and ad networks and don't have to feature the Blogger navbar. Actually, you don't have to feature the Blogger navbar if you aren't afraid to do a little template tinkering, but that's not the point. Big blogs like to be hosted on separate platforms because they have more control. Those big hosting platforms still come at a cost, so you better be making more money than you're spending in order to use one.
There's nothing stopping you from starting out on Blogger and taking advantage of free. You're not going to become the next Internet sensation overnight, so you don't need to spend all your money on hosting fees. Your archived blog posts can be moved wherever you need to move them when you strike it big. Your feed can transfer, too. The barrier that holds a lot of people back from starting a blog on Blogger is actually another misconception. I've heard many people tell me they didn't want to use the platform because they knew Blogger didn't let you use your own URL.
Not true. Blogger has allowed custom URLs for quite some time. And as it turns out, registering your URL through Blogger is a bargain. A custom URL with WordPress.com is $12-$24 as of this writing - and they still force you to serve their ads on it. A custom URL with Blogger is $10, and you don't have to put any ads on your site. If you do put ads there, they're ads you profit from.
If you register your blog from scratch today, you'll go through a dialog that asks if you'd like to set up a domain. If you're editing an existing blog, go into Settings: Basic and choose +Add a custom domain. You can add either add an existing domain you've already registered or register a new domain right on the spot. This is really the better option. It only costs $10 and is pretty easy. Payment goes through Google Wallet, and you can choose between two registrars (this last option is useful if you're not a fan of GoDaddy, which is the default registrar.)
For $10, you get a custom domain for your blog, access to Google Apps (this is useful if you want a professional sounding email address attached to your domain) and all the privacy features enabled. GoDaddy and other registrars often charge extra for "privacy," so the $10 is a bargain compared to the price of registration plus privacy.
There you have it. Free hosting, ads that potentially make you money (if you want to show them at all), and cheap domain registration. All this makes Blogger very appealing to the savvy new blogger.