It’s pretty tasty, to me at least. But I like mushrooms so YMMV. That said, it’s not overly earthy or eating a bag of shrooms. If you ever, as a kid, saw a tin that said Hersheys on it in the cupboard and grabbed a spoon; well, it’s like that, but a little better. The cocoa in it is what gives you the caffeine bump IIRC. Assuming the ingredients are legit, then there is good stuff in it, but I think this is really geared toward another group of people than anyone trying to curb coffee. If it was cheaper, I’d drink it every day.
To answer the question, sorta, you could grind a batch of lions mane and chaga and have at it. This has other stuff in it to for palatability, but like you said, you could make your own variety if you want. Again, assuming the ingredients are accurate, it would be good for you, as long as you can manage to choke it down.
Manage your finances. Know where every penny goes. Budget as best as you can - plan for all of the things you know you spend money on through a year. It doesn’t mean you can’t spend money on things you like, but it does mean that you know when you can afford it. It gives you confidence and control no matter how much you are making.