Take a look at the Monday box in reboot that you can purchase. The pet has a 10% chance to get and you get 3 chances for 25k.
That gives us a estimated cost to get a permanent pet a roughly 83k. Compare that to the standard pet boxes that come around in rotation that
have a 7.5% chance at a perma pet for 4k that gives an estimated cost at roughly 53k.
Not sure how these boxes are a deal at all for trying to get a permanent pet.