Ran,
A lot depends on the soil under the sand cap. Additional drainage work may be needed if the soil is very dense. What I've seen done in AZ is an 8 in. cap.
If a golf course is 90 acres X 43,560 = 3,920,400 sq ft. If your only going 8 inches then you could multiply that number by .66 to arrive at cubic ft. 3,920,400 X .66 = 2,587,464 divided by 27 to arrive at the # of yards needed = 95,832. If you were extremly lucky and had a quality sand source nearby, you might get that kind of quantity for $10/yd = $958,320. Add in the cost to spread it and you have a general idea of what it costs to cap a course. The nearby sand source is the key.