Depends... the cheapest I got were R2000 p/m for 2m on a mast and then *average as above. I know places where it costs R2000 or more per antenna/dish/box or any other item. Not in this game anymore, just a private WUG.
*The average really depends on your location and I only know about rates in the Western Cape. Perhaps you can ask PTAWUG?
I put a dish on top of the No 2 Military Hospital in Wynberg. The hospital administrator "facilitated" the roof access. About 4 years later, I get a call from SANDF in Youngsfield asking if I paid for the electricity it used. So I went there and took it down, never paid a cent.
They will charge you based on the wind load your equipment places on the tower, plus a flat rate. Last I saw 3 x 2m antenna and 3 radio units was around $2000, not from American Tower though