Sometimes we'll use a pole pruner ("chainsaw on a stick") We stick it right into the loosened ground and it cuts the roots nicely.
Then maybe a few swings of an ax and then they come out pretty easily. Yes I do admit to using the truck on a few occasions but I dont like to do that for various reasons...not the least of which it does look unprofessional.
I give them a "not to exceed $x " price and I make the number much higher than it usually turns out to be. Predicting the time for shrub removal can sometimes be as difficult as estimating a property cleanup