As someone who listens to audiobooks at work, I like the idea. But...
I listened to some philosophy 201 course years ago. It was too much, in that the ideas I didn't agree with formed a "yes, but" reaction that I had no way to resolve. The traditional route would be for the students to get together and hash it out over coffee or beer. But this isn't an option for audiobooks, and I found it unsatisfactory. But this could be just a manifestation of my contrarIan/argumentative nature.
If you were to do an audiobook, and if done well, I think it would be great. Consider including a .PDF with the charts. Ideally with hyperlinks at the chart for the point in the audiobook discussing the charts. This would help the reader treat the book as a reference, as was intended.
In fact, the .PDF could be used as advertising for the audiobook, with the hyperlinks going to short segments of the book, and the audiobook being for sale independent of the free .pdf.
Using all methods for broadest dissemination, makes sense. But there are already plenty of other options for getting the frugality message out there. If it were my book, I doubt I would be motivated to do all the work of changing formats to reach more people less likely to receive the information in an actionable way. There is definitely a diminishing returns issue to address.
Questions and comments