A 9 hole par 3 course can be built over a very small parcel of land, you can get a full size 9 holer in less than 10 acres, I have just done one in 5 acres but the holes are kinda 65-120 yards long. Greens are about 1/3rd the size of a normal green, I am hoping to build for £100,000.
Only thing I would say is that golfers/members don't really want to play them, the percentage of play compared to 'real' golf is very small mainly because members want a full game, those that do enjoy them usually live close and use it as part of their practice, or visitors wanting extra golf so quite good for resort golf.
Ideally if you are thinking £$£$£ they need to be easy so beginners can enjoy them so you could monetize them as a separate commodity. Almost like the next link up from Adventure golf.
You can still do super funky greens, one of the holes I am doing gathers to one spot on the green, its down hill and literally if you can hit the ball you could get a 1 if the pin is in this location.