I already have several copies of the 2nd print; along with several copies of the 1st print.
I never paid over $40 for any of them.... most were less.

Of course, putting it on E-Bay will probably get you more than $40 these days.
Despite so many listed for that and more, I cannot see it getting $80.
Good luck.

$80 seems high.  The copies with the extra mythos are not really that rare and generally overpriced on Ebay and elsewhere.  They often also stated that they were "banned" which is also untrue.  

Looking on the shelf, I have 3 first prints and 5 second prints - I have never paid more than $20 a copy.  If you are a patient collector these are not hard to find.  I have sold a few with names inside or in poorer condition than I would keep for more though.