Price: A pack of Tim Tams is about 3 AUD, which is currently valued almost 1:1 with the USD. If you're flying to or from Australia or New Zealand, or even Asia, you can cross your fingers to get them free as a snack on your flight.
Where to Find It: If you're in Australia, you can practically bathe in a bathtub of Tim Tams after a quick visit to the corner store; they're everywhere and in abundance. In Canada, you should just check out your local major grocery store. If in Asia, keep your eye open for grocery stores or mall specialty shops that cater to expats. If in America, you've got it most difficult because Tim Tams usually like to reside in the "British Foods" section of grocery stories that are pioneering enough to have such a section. We've never found a shelf dedicated to just Aussie products, so oftentimes the Tim Tams get branded as UK.
[Update: @kimb0lene just reminded us on Twitter that Pepperidge Farms is doing Tim Tams in the USA, so take a closer look in and around the Pepperidge Farms cookies area, and don't get sidetracked by minty Milanos.]
[Further Update: @ajmoreland has convinced us on Twitter to include the awesome Tim Tam Slam move. Here's how to do a Slam: bite off each end of a regular Tim Tam. Put one end in a hot beverage, like cocoa or coffee or a latte, and suck the drink up through the center of the Tim Tam. The creme melts and comes up with the drink. Just be sure to eat the rest of the Tim Tam before it starts to melt, too.]
Pro-Tip! When you're in other countries (like, say, Indonesia) and hungry for Tim Tams, don't shy away from the more exotic flavors, like cappuccino orOMGcheese!