Agree about Pakt, but not about $50 self publish per se (nor the tenured prof remark). I am in the process of writing a code book, but it is compiled via quarto so at least you know the code works as expected.

This is my favorite helpful advice for pricing, https://pubsonline.informs.org/doi/abs/10.1287/mnsc.2020.360.... Estimate max someone will buy, then divide by two (assuming no marginal cost, like e-book).