Yes, you can find a job on your own. But not all jobs are the same. Maybe they'll find you a better job.
Yes, you can learn on your own. But I don't think there's any question that a good teacher can help you learn faster.
gSchool is new. So it's too early to find hard evidence either way about the quality of jobs you'll get, etc. But if they give you the right teacher, education can be a good investment.