i think it should be less expensive for expand stable scrolls because you only get an additonal 20 i think i think it should be near 15000 silver

here is the thing. when you have many lvl 50 pets, it is very easy to get 15000 silver in an hour, not even a day. by making such an item that is currently valuable dirt cheap, the game might as well not even charge you and allow you unlimited space in stables.

Also, how would the game make any income if the main reason people buy gold is to expand stables when they run out of room? Forget paying the game developers, who would pay for the server costs to keep this game up and running?

And since there is already several different alternatives (exhibitions, weekly charts, custom skin popularity, bug reporting) to get gold in-game if you don't want to spend real money, I see no reason to change the current set up.