"There is an upper end, but it appears to be very high, well over $500/round. Golfers tend to be wealthy and are willing to pay top dollar to play a course perceived as world class. There is just a ton of demand."
Wayne K. is right about this. No doubt the top high-end course have higher overhead expenses than a typical local/regional course, but I doubt the expenses are greater by a factor of 3 or 4 times.
After all, does it cost 10 times as much to produce a $500 bottle of wine as it does to produce a $50 bottle?
This is the correct response. High end courses generally have higher maintenance budgets, because their customers' expectations are higher, but it probably isn't triple the other good courses in the area. However, the payroll inside the clubhouse might be 3x or 4x, and that's a factor, too. You pay for "service".
Many of these courses have bumped the rates up considerably when they get to a higher status in the rankings, so in that respect it is very much like a luxury good. And that's the chicken, the egg of higher prices generally follows status, instead of being the leading edge.
Note to Sean A: the member guest rate at these famous courses is getting pretty high nowadays, too, precisely because they look at Pebble Beach and Pinehurst and say, why don't we charge that, too? Memberships are divided on whether they'd rather be able to bring guests at a reduced rate and pay more dues, or gouge for guests and pay lower dues.