I took one about sourdough baking. I must say, I learnt much more just by reading a book (book was also about same price). Cooking classes at least in my country tend not to be that scientific or really explain why something happen. Books answer on that better. In my case, the teacher was homecook, who did the bread her mother did and never questioned if there is better way or what are options to modify recipe and how that affects to the result. So there may be a lot folk lore type of knowledge, which isn't always right under our current science.

But some people like the idea they does things as it has always been done and feels like it is more authentic, or just simply don't have enough interest to read a 200+ pages book, or likes social aspect of cooking classes, which is understandable.

I personally prefer books for learning and then I practice in home with knowledge I learnt and with videos on youtube to see how professionals does it. Also books are pretty.

If there was something very special and highly localized about a food product that is hard to find information on, then maybe a class from a local who makes it could make sense, but for basic french stocks or sauces, or kimchi, for example, nah.