Tom,
At most full service resorts, almost no overnight guests are paying the full rack rate due to buying a package that includes room, golf and sometime food and/or spa services. (The following is a list of top courses where I have effectively paid less than $50 for a round: Prince Course, Whistling Straits, Irish Course, Barton Creek, Poipu Bay, Kauai Lagoons, Deacons Lodge, Wynn, Harbortown)
In many cases, the economics of the resort is that they are using either the hotel as a loss leader for the course or vice versa.
For late afternoon rounds, there is a totally different target market, often non-resort guests or locals. These people have many more options and courses need to charge less in order to compete.
In reality, the rack rate on most resort courses is actually too low and the shoulder rate is too high.
Back to the original point re: negotiating, the real question i think is, should courses just lower their shoulder rates instead of encouraging negotiations?