I have never been anywhere near the place, but wouldn't Fisher's Island, with no fairway irrigation, and thus giving rise to less weeds, disease, fungus, etc, stand a good chance of coming in under $700k?
And there seems to be great bifurcation (or trifurcation, etc.) in the golf world vis a vis maintenance budgets. There are the top 5 or 10% that spend $700k, $1MM, etc keeping up with the Jones, but for everyone of those, there are at least as many Mom & Pops that can achieve 90 or 95% of the results on $250k a year or thereabouts.
In a dream world, it would be nice to see courses in the Top 100 set a good example for the rest of the courses, and in that respect I tip my cap to Fisher's and their resistance to installing fairway irrigation.