Enormous Build Size! Help?

Hi, I am building a game for iOS and it is going well. I just finished it.

But when I ran it on my iPhone i noticed it was going quite slow at times. Taking 0.5s to load the gameScene. It made me wonder. So I opened the Editors Log after build and saw that the entire game build was on 200mb. And that my sprites(characters) took between 10-40mb each. All of the .png files I am using for my background, player and 6 enemies have the total size of 2.5mb.

So why does Unity increase the size of my character sprites from 0.5mb all the way to 10-40mb?

I really do not see why, please help me.