A retired stock broker who operated a crane in college decided to buy one to have something to do. He got a 35 ton Altec with 127 ft. of main boom mounted on a '05 Sterling. The cable is inside, and with that 127 ft. he can still manage around 3000 lb from 75-80ft away.
Brand new with spreader bar, timbers, plywood, slings, chokers, etc. the whole package was just under $200,000. At the moment he charges $100/hr. to set trusses, and $120/hr. for just about everything else. He can definately operate the machine safely, but productivity in tree work is an issue sometimes. I think that's why his rate is usually about $15/hr less than the competition. However from what I've seen that machine do so far, I'd say it'd be hard to beat overall. Just make sure that the operator matches whatever you get. There are some trees (mostly sprawling oaks) where we go for the competition because they can pick it much faster than he can with the same set-up. I'm talking 2hrs difference between the two operators.
One thing to consider also is set-up. This machine has to be perfect for the computer to behave right. I've seen a 25 ton boom truck get into places this thing would never go. From the looks of the pictures that you've posted in the past, it seems that your business is in tight residential areas. A bigger machine isn't all that great when you can't get close enough for it to be of use.
I'm sure you've thought of most of this, but said it just in case you haven't. My father-in-law is retired with little to do. I've been trying for the last year and a half to get him to think about buying a crane. His son is a carpenter and could hook him up with all kinds of truss work. Add that to the 7 or 8 crane jobs I do per month and it's a no-brainer on finacial feasibility.
TT