The quote "There are times...when one must lose a little beauty if one is to keep what little beauty one already has," from "The Flying Machine," by Ray Bradbury, is a paradoxical statement. The Emperor is responding to his desire to keep things the way they are in his kingdom in ancient China.
The flying machine, invented by the man who is brought to the palace, allows mankind the opportunity to enjoy the world's beauty as never before. However, the Emperor is fearful that someone might use the machine for something other than its access to the world's beauty. For instance, someone might try to fly over the Great Wall of China, an evil intent as the Emperor sees it.
The Emperor also does not want the word he knows to change, so he is willing to sacrifice the beauty brought by the flying machine to preserve the world he so enjoys—in the beauty he has created and maintains, especially in his invention of the mechanical box with the miniature trees and birds within it.
He was saying that we don"t need all of this and that to make beauty the little we have is ok. The lttle we have is what makes us even more beautiful.