You should understand what I charge in Detroit, vs an irrigator in Texas, vs an irrigator on Long Island, Cape Cod, California, Nevada, Minnesota, etc... has no bearing on the going rates in your region.
You will get better and more accurate information anonymously calling irrigators in your neck of the woods for pricing. I'm sure those will fluctuate based on who you talk to, and for a variety or reasons.
For that matter, ask your client for the rates he has been paying. Tell him you would like to know this so you can match them...or reduce them by a percentage.
You'll need to spend a little more leg work on this than making a post on a thread.
Good luck to you.