I'd say it's quite high. However, I'd echo that if one is coming at building a boilerplate while simultaneously wanting to learn and understand all of the concepts in the stack, I could see the boilerplate taking more than an hour or two.

(For example, I've seen some that implement some custom Redux middleware simply so that there's a conceptual reference right in the boilerplate as to how one would be done).

Are you thinking of getting into it? I heavily advise checking React out. I think it's fantastic!