Bought all of mine ages ago. The only one I have actually had drop for me was Ji-Kun, on a token roll a few months ago. Sold it for 3k or whatever the going rate was - not much of a reimbursement on the 20k or so I paid when I originally got him, but that's just how it goes.
As someone else suggested, though, if they really are going for 15k on your server still, you'd be much better off making a trade alt on another server and amassing gold there. Trying to farm them all yourself is only going to cause frustration. Remember the drop rates are so low because thousands and thousands of people do these raids, and only a fairly small percentage of those care about pets.