Correction: You get 4 coins.
I came here to see if this would answer my question, but it didn't. When you look at the box with the fruit in it that is next to your pony, there is a small 1 (or 0) in the bottom right corner. This leads me to the conclusion that your tree can grow bigger and produce more fruit per day, and also when you look at the outside of the farm (not in the window that pops up, like to the left of the farm in the first picture) there is a large tree. If your tree can grow bigger, I'm guessing you make it grow by reaching a certain number of friends, or by feeding a certain amount of fruit to other peoples' ponies, or perhaps a combination of the two. So my question is, how do we make our trees grow, if they can?