No. Those numbers above are ill-informed.

But yes, the average print costs for a single-color book per unit are in the 2-4 dollar range (that is, manufacturing alone, no design, marketing, editing).

And how would it be possible for Amazon to "keep their lights on" selling physical books at 40% off list price, if they pay O'Reilly $36 for a $40 book? Amazon buys from O'Reilly and most other pubs at 60% off, non-returnable. So the math for the publishers' take from Amazon on physical books looks like this:

[list price] * [.4] - [print costs / overhead] - [author royalty]