mallyh - "haven't these celebrities got mirrors surely they can see how monstrous they look after extensive work ."
Mirrors work the same for everyone, from the gorgeous to the plain, the rich to the poor - we look in the mirror and zero in on the bit of our reflection that we dislike the least, and ignore the rest.
Plastic surgery is about self-image - it's what YOU think you look like, not what other people see, albeit that their view is more honest and objective.
So from all of us who make an effort with our outward presentation to the world, from a shave for men to a little make-up for women, right up to the extreme and frequent alterations of the dysmorphia sufferers, the motivation is exactly the same - to present to the world an image which we believe they see, and we are reasonably happy with.
Of course, everyone else sees what they see, which may in some cases be far more positive than our own version, but in the cases of celebrities with 'work done', they rarely look as presentable as they would wish, or that justifies the pain and money involved.