Okay. To some extent that's fair, but on the other hand "opportunity cost to society" is just a fancy way of saying the same thing as "how daunting of an invest

Okay. To some extent that's fair, but on the other hand "opportunity cost to society" is just a fancy way of saying the same thing as "how daunting of an investment was that" so the quoted statement is hardly in disagreement per se :) Of course, there are also plenty of alternative measures available at the linked site which could be better than either percent-of-GDP or CPI. (I'm leaving their use as an exercise to the reader...)