Your late father in law had excellent tastes and must also have had a very good knowledge of what he was buying. Max Pupain, while superb is not now so well known despite being one of the best Australian fine art photographers.
While I can't put a market value on these idividual images they must each have a market value well in excess of $500 (us) per print. You could probably get a better indication by going to the Print Room at the Photographers Gallery in London.
This is a great little collection.