I have a similar experience, but precisely because of this I am very careful to check the formula each time I have to type it. Mistakes in the formulas are not "just typos", they are a very annoying and potentially harmful kind of typos, and we must take great care in order to avoid them.
Like I said above, "typos" in sequences of calculations are obviously problematic, and lead (almost always) to mistakes in the final result. In this case that's not applicable since there's no "second arithmetic manipulation" following the typo:ed one. (The author replaces the incorrect one with the correct bayesian equation in the next section.)
