The sale started yesterday and will continue until January 4, 2016 at 11:59 p.m. PST.
Get the WoW Battlechest for $5, and if you're feeling adventurous, WoD for $12.49. I don't believe WoD is necessary to RAF yourself for the rewards, however.
If purchasing during the sale, the total cost for one RAF pet is $35 (minus the value of one free month of game time that your main account will receive). The total for all 4 RAF pets (Zipao Tiger, Silver Pig, Golden Pig, and Jade Tiger) comes out to be $140.
I wrote up a blog post a while ago that details my experience RAF'ing myself. It's an old post, but I think everything still applies. I've also included some updates about the WoW Token and other things.
In addition to this sale, don't forget that Brightpaw will be coming to the Blizzard Store December 2 of this year. Up until the end of December, 100% of the proceeds will be donated to the Make-a-Wish Foundation.
Lots of holiday pets coming up! Tis' the season for sharing the love of pets. :)