Hyacinth Macaw used to be big business and gold for anyone lucky enough to have and to sell one. Nowadays they are a zone drop and are more abundant around the Auction House. The drop rate is still muted to be very low at roughly a 1-5000 rate but more are seen on the Auction House.
I managed to pick one up from the Neutral Auction House for 2,000g, this was a steal..... or so I thought. My beancounter also said so, showing trading at around 18,000g (this was a couple of weeks ago). I sent the Hyacinth Macaw to my bank alt and checked the Auction House, to my horror 3 or 4 listed at under 5,000g and I was very sceptical about buying them all up so I decided against it. I did think that it may be a rush of blood from the people who stocked them at the end of WotLK, maybe they had read Wowhead/Warcraft Pets about drop rates so I waited it out for 2 weeks until the madness had died down.
I listed mine this morning for 14,000g as someone had theirs up for 20,000g and sure enough it sold. Thats a nifty bit of gold making.
So, to sum it up. Check the pet prices on your server. If your beancounter or any addon you use to track the Auction House is working you can see the prices over the last two weeks. Some are really good gold earners and there are a few bargains still to be had.
I have a post for pet's planned for the next few days in which I would like to elaborate more if I can gather enough information together to make it respectable.
Have fun /auc getall scanning o/