I graduated from cosmetology school a year ago last week. I've been working for almost 4 months (took a 6 months between graduation and taking my state board to stay home with my then newborn son) and I can honestly say I made the right career choice. I love what I do!
I found school very rewarding, but I think a big part of it was that I had (still have) a great passion for doing hair. The school you choose can also make or break your experience. Take a tour, talk to the instructors and students.
My tuition was about $6k, but they raised it after I graduated because they received a grant that would allow students to get financial aid. I got lucky, I think. I also live in a small area where most things are less expensive than other places in general. I think tuition at my school is now over $10k And schools in the closest larger city tend to charge between $15-20k.
Just a heads up: Most schools will heavily focus on teaching what you need to pass your state's board test. You'll pretty much learn the basics, which are good to know. But, if you want to do something like braiding make sure you ask the instructors if that is something they focus on. I went to a school where I was the first black person to enroll. And it's in an area where black folks are scarce and they don't typically go to the school to get their hair done. So, I had to practice/learn a lot of things on my own. Word got out that I was there, so a few people came to me which was great experience.
Anyway, I say all that to say yes, cosmetology school is worth it if it's something you really want to do. Also, depending on where you live you may have to be very self-motivated. And expect to spend at least $10k depending on the area.