The pets cost £9, $10 or €10 apiece. Half the proceeds from sales of the Pandaren - the first incidence of Warcraft's joke race of kung-fu pandas in WOW - will go to the Make-a-Wish Foundation charity if you buy it before December 31st.
It seems even the biggest subscription haul imaginable doesn't make Blizzard immune to the lure of micro-transactions. This is the first time the company has offered in-game WOW items for sale for real currency, although it has been ramping up the sale of services such as race changes and faction transfers of late. It can't really argue the cost of the pets is a deterrent, though.