TCG Loot card mounts like the Spectral Tiger have been BoE for a long time now (since patch 3.2), and that was and continues to be well-received, and as far as we've been able to tell hasn't had any adverse impact to the game or economy - despite them selling for sometimes astronomical amounts of gold.
It’s potentially worth noting that no new gold is being introduced into the game's economy with those mounts or the new Guardian Cub pet.
Our goal with the Guardian Cub is to provide alternative ways for players who don't want to spend real money to add these pets to their collection. Even though this has been available a while now with the TCG mounts, this is obviously a new kind of way to deliver Pet Store pets, and we're definitely interested to hear your feedback and ultimately see how this will play out.
I think since the Spectral Tiger is really rare it shouldn't be compared to the $10 pet in the store that anyone can buy. Also I have only seen 1 person try and sell it for gold, the rest sel it for hundred's of real life money.
Also how is "new gold" being introduced into the game when buying from a gold farmer. All they do is farm the gold that is in the game then sell it. I don't think they create new pixals of gold and sell it. They farm what's already in the game.