Wayne,
Just back on the GCA site for a moment. A couple things;
1) If you are not re-building the entire green, the cost of course would be less. However, in the area you are softening, you will have to do work well out into the surrounds to tie everything together. For example, you can't just take the back of a steep green and lower it without going into the back surrounds. I guess you could do that, but it would probably look goofy. As an example, think about a spine coming into the back of a green. You can't just lower the spine at the green edge and forget about the rest. Everything should tie together to get it looking like that is the way it always was. The cost to do this work is tied to the size of the area of disturbance, 2) The cost for a "new green" might be $50,000. It might also be $35,000 or $135,000 depending on the size. A 5000 sq. ft. green costs a lot less than a 8000 sq. ft. one. Material of construction also has an impact. 3) Another added factor is how accurately you want to map the area of disturbance?
These things all add to the potential cost. Again, the extent of the work to be done is probably the biggest cost factor.