I'd say based on this being a very exclusive club, plus the well-dressed look of most of the caddies and the general fees of the time, the club probably charged a buck per round of 18; of that, maybe half actually went to the caddie. With good service (resulting in good tips), a caddie may have actually made a full dollar per round.

For reference, I found information regarding caddy fees at Inverness from the early 1900's, which stated "The book listed caddie fees of eighty cents for eighteen holes, forty cents for nine holes, and thirty cents per hour for chasing practice balls."

Baltusrol Golf Club is a 72 hole private club, this photo must have been taken on what is now the Upper Course as the Lower wasn't built until 1922.
The course has held the US Open 7 times and the PGA once.
According to their website caddy fees are $70 per bag, wonder how much these guys got?