What are star gems?
Star gems in Habbo are something you can give to another Habbo to show you like or respect them. You can see the amount either you or someone else has in the user profile. When you run into a Habbo you like or even a famous one with a nice outfit on, you can give them star gems via their user profile.
Why do they cost Duckets?
That gives them more value, as people can’t go and hit the button endlessly. This also means that the star gems you have received from others have more worth than if they were unlimited.
What can I do with them?
Nothing, except enjoy them! Star gems are not a currency, nor can you give them to another Habbo.