I see that we can buy a Tree Fort in the store for 450 gems. When this building is upgraded to level 10 it will give 10 million defense. But I already have 42,127 million defense, so it sounds to me like an increase of 0.000237% for my 450 gems.

It seems to me that any defense building is completely worthless, and has been for a long time. The only thing that a Tree fort is good for is to hide another building. But since everyone knows that, they always look there anyway.

I suppose I would buy them for gold just to have more hiding places, but they are not worth any gems.