be (like) a bird in a gilded cage
To live a life of wealth and luxury but to be without true freedom, happiness, or contentment. She married her husband because of his fortune, and now she is a bird in a gilded cage, living her lonely life inside their empty mansion with a man she does not love. John forsook his friends and family in the pursuit of his riches, but with no friends or loved ones, he is now like a bird in a gilded cage.