If you do the dailyquests up in Argent tournament (WOTLK content), some of those rewards a bag with 10gold, + their natural 15ish gold, + a badge.
Combine 40 badges for a pet worth around 5k gold on a populated server. The badges also goes into your currency tab, so you should not have a problem with beeing flooded here, as 5-6000 badges will not take up any bagspace, and there is no time spent disenchanting anything.
The pets will however fall in value if you were to post 10 of one specific pet, but then again, there are 6 different pets to choose from (one from each faction, + 1 neutral one), so you should be able to spread this around a bit.
However, if you are extreme, and end up with like 200 of each pet, I guess it would be hard to flog them. Well, there is kind of a solution here as well, you can use the badges to buy Weapons and other shit as well, which can be vendored for more gold. You can also buy BoA gear for these badges if you need.
Check this site for reference in case u want to know more of the stuff you can buy
Champion's Seal - Currency - World of Warcraft