I had quotes upward of $1000. Decided to do it myself. Place it somewhere where it is easy to service. At a minimum, you will need to start it up, clean it once (min) at midpoint of summer and close it down. Pain in the but if 15ft high lol.
I've done my fair share of servicing swamp cooler. Just afraid that I will install the flashing wrong or drop it while getting it on the roof, so I want a professional to install it.
They are bulky, and kind of difficult to move. Don't blame you for hiring contractor. If I had a good person I would share, but like I said, those I talked too were too expensive for me. Good luck! Cheers!