I honestly hadn't thought about that. I just want to avoid digging 120 plus holes, and make it easy for my wife to do the same. She will like being able to plant a tree herself.
Let's say I have someone come out to my house 20 times over the next 2 years, and each time ask them to dig 3 18" holes for trees and 3 for shrubs each time. So 6 holes per visit. No more each time, because I have to run the irrigation hose each time using a modified subsoiler to create the shallow trench.
My final cost for the Auger will run about $600 over 2 years if I choose to sell it for $300. So 600/20 uses = $30 each. Call it $5/hole. I couldn't hire a pro, but I suppose I could hire someone for $30 for that work. It just doesn't seem appropriate. When I hire a landscaper, I try to minimize their trips out to my place as much as possible, but for this project, we won't be able too.