Solutions to 16m extortion Plots....
16 meters is basically 4 meters by 4 meters yes? Build 4 walls around it as a penacle of your land build. Extend this build up 200 meters to the limit of the land tools to eject people. Now effectively you have "Surrounded the culprit"
Prim usage...80 prims
4 prims per level @ 10 meters high
20 levels high.
Each level would be 10 meters high and 4.2 meters wide using 4 prims per meter.
(Yes a single prim could effectively do the same thing yet the center would be over the offending partys land and thus would allow the structure to be deleted.)
Additionally...make the inner texture transparent so that the offending plot could see out but you wouldnt have to see in..

Benifits to Society would be.
A. They could be used as flight level traffic lights annotating the height of the sim repel functions on the land.
B. They could bring in Income serving as Towering Bill Boards.
C. Additionally it could be a Mini Tower Mall. Build Platforms at each level and sell Space for Vendors to place their wears. (Actually if you hollowed each 10 x 10 cube and turned it on its side the platforms would be made and cut the cube in half to form an L. )
This would effectively kill the extortionist cause it would do the following.
A. its a big finger pointing out hey a dumbass is trying to extort the land value
B. 4 meters square is very little room to do much of anything in.
C. Who is going to fly down a 200 meter tunnel just to see the price of the land.
Noted: this is only effective if the land is for sale. If it's not forsale and the owner has no build on it. I would not suggest the aforementioned method as they may just be using it as prim land. If they are they may be willing to swap for one on the edge of your land versus one in the middle of it.
Sincerely, Shadow Weaver