A location would help. With that said the age of the pivot has no bearing on it. It’s basically custom work. As long as it gets the job done that’s all that matters. I’m trying to visualize how a 40 acre pivot is going to be big enough to cross over and do another 30 unless it’s towable or a linear. HERE I charge $35 per irrigated acre plus utilities (or fuel, oil,etc). Probably should charge more with what stuff costs now. But if it makes it more convenient then it’s worth something.