Culinary school is worth it. Which school you choose and how much you pay and how you pay will all be different depending on you.
But if you are seriously interested in a career in cooking, then you should do some research and go to school. Make sure the school is reputable, has been in business for a long time and provides a good education for the money. You will figure this out as you do research.
Whether or not it pays off depends largely on you. Many people go to all kinds of schools, get diplomas and don't learn much.
Whatever school you attend, take it seriously, study hard and pay attention. Remember that the best schools can only introduce you to culinary topics. You will still need experience. Schooling is only there to give you some insight into how to learn and what is important.
The theoretical rule I was told is that someone with a degree will learn in five years what someone without a degree will take fifteen years to lean. But again, that is largely up to the individual.