Thankfully, this lack of information was a bug that has been resolved:
If you're interested to see what a Guardian Cub is selling for on your server, the website AH Spy has set up a convenient Guardian Cub pricing page showing the market value of the pet on each server, both US and EU. As you can see, prices vary wildly. The Cub is as cheap as 5,000 gold on some servers and as expensive as 100,000 gold on others. For the most part, though, a Guardian Cub can be had for just under 10,000 gold.
Maximize your profits with more advice from Gold Capped. Do you have questions about selling, reselling, and building your financial empire on the auction house? Fox and Basil are taking your questions at firstname.lastname@example.org and email@example.com.