Hiring a carpenter to build a custom closet can cost several thousand dollars. If you are not in a place to have a custom closet built, consider modifying a store bought one. In the latest Domino issue, there is a fantastic article on transforming an IKEA Pax wardrobe into a very custom looking beauty. It is a great example on how good design does not have to be expensive.
Here are some other great Pax wardrobes that have been modified to look custom.