I've got 575 level 25 pets and even more that I've level up to 25 that I've sold or traded and I have to disagree with you. The stones grant a single level for a single pet. They would need to be common as dirt to have any significant impact on leveling up your entire pet collection. They are currently showing as BoP so you won't even be able to buy up a stack of them to quickly get your first pet to level 25. In the end they'll just be an occational extra level while working on a long grind.
1545 pets
I've got 575 level 25 pets and even more that I've level up to 25 that I've sold or traded and I have to disagree with you. The stones grant a single level for a single pet. They would need to be common as dirt to have any significant impact on leveling up your entire pet collection. They are currently showing as BoP so you won't even be able to buy up a stack of them to quickly get your first pet to level 25. In the end they'll just be an occational extra level while working on a long grind.