What you're seeing is actually pricing for our automated testing service. Sauce for Mac is either free (30 mins of testing/mo) or $12/mo (for unlimited minutes against all browsers). It also comes included with all the testing plans on that page.
Whoa, this is news to me, I checked out sauce a month or so ago and came to the same conclusion as highwind. $12/mo is something that I would be more interested in. You should make that way more obvious. I haven't fully harnessed the power of TDD and it isn't used at my current job so I have no use for it. On the other hand the ability to test websites on different browsers is very important to my job and for $12/mo it's something I can afford to get for myself to use for work and personal projects.
This needs to be clarified on sauceio.com/mac. It's very confusing right now to go to pricing and not understand what it's for.