i get where you are going with this, but the way i see it is, there are basically 3 types of people that buy serious monsters and they are; a) the un-informed or b) those that have a monster tank / pond and want to fill it with monsters and c) those that want to show off but are unequipped to do so...
So if these cute 2" monsters arent at stores people with no clue wont be as likely to impulse buy them, since they wont see them, and those who do want them, have likely done their research in order to even know about the fish, and therefore will be prepared to house them...
And as for those that want to show off, again, if they arent in the stores, they arent as likely to purposesly order one just to own one...