Short answer: Yes, it is worth it. Easily.
However, I think it's a very healthy attitude you have, to consider the worst possible scenarios. Chicken keeping isn't a hobby like painting or motorbike maintenance, when if things go south you can just say "the hell with it", and leave everything to gather dust in the basement. Chickens are living, feeling creatures and the moment you acquire them, you also acquire the responsibility to keep them healthy and happy for the rest of their lives. An "it will never happen to me"-attitude is a terrible starting point if you want to keep animals.
My parents have chickens, and I think they have the wrong attitude about it. They don't mind picking up poop, feeding them and gathering eggs, but when the chickens get ill, they cop out. They aren't prepared to one-by-one catch a whole flock to administer medication to them. They aren't prepared to daily swap a bandage on a shy bird with bumblefoot. I'm always the one who has to take care of the difficult stuff.
But I don't mind doing that. If you truly love your chickens, you're okay with doing messy, disgusting, time-consuming, expensive, even painful treatments, because you know it's for the good of the birds. (What I do mind is that most days, I don't have time to visit the chickens, so I really wish my parents were as passionate as me.)
And, even though you should be prepared for the worst, fact is that statistically, your chickens will for the most part be healthy. I myself have in my decade or so in chicken keeping never been hit by the worst diseases, such as red mites, Marek's disease or ILT. And the problems I have had, such as frost-bitten combs and scaly leg mites, have been easily treatable.
Another thing to note is that an ounce of prevention is worth a pound of cure. Make sure to buy healthy individuals (personally, I find that purebreeds seem to be the least healthy...) Keep your coop clean (easy if you clean a little every day). Provide fresh water and good food every day. Let them free-range as much as possible; as with humans, chickens are healthiest if they get a lot of exercise, and free-ranging lessens the amount of poop they step in, increases the variety of their diet and, last but not least, keeps them entertained. There are dozens of ways you can tweak your coop and pen to make them more chicken-friendly, but that's a topic for another thread.
In short, it's definitely worth it, but keep learning as much as you can and prepare yourself as best you can for the worst possible scenarios.